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Converting a colossus: Building conversion and conservation at Lots Road power station

Duncan Hawkins

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    Since 2007 a programme of decontamination, selective demolition, internal alteration and building recording has been under way at Lots Road power station (TQ 2640 7700; Figure 1) to advance conversion as part of a residential and mixed use development. The power station was for some eighty years the principal source of power for the London Underground. The conversion will see the retention of the external walls, steel frame, chimneys and selected internal steelwork of London's longest serving power station. The scale, structural details, age and condition of the building present an almost unique challenge in the field of historic building conversion; perhaps matched only by the much more recent Battersea and Bankside (Tate Modern) power stations.

    Historical context

    The creation of Lots Road power station owed much to the ruthless drive and ambition of the notorious American businessman and financier Charles Tyson Yerkes (1837-1905)1, who in the early twentieth century first attempted to unify London's (then) chaotic underground railway system. Yerkes had been a driving force in Chicago's street and elevated railways where he had sought to create a monopoly from 1886 onwards. Something of Yerkes' character is perhaps reflected in contemporary comments. Chicago Mayor Carter Harrison Jnr wrote of him, 'Trained in the public utility school he saw a roseate future ahead for the man who would apply eastern methods of official corruption to the crude halfway measures so far practised by the novices in Chicago's best financial circles'.2

    In 1899 Yerkes attempted to secure a no-cost extension to one of his Chicago street railway line franchises by the simple expedient of handing out nearly $1 million worth of bribes to City politicians and officials. Yerkes' bribery attempt failed however and he left Chicago for New York in 1900 politically and socially ostracised.

    Meanwhile, across the Atlantic the opening of the City and South London Railway in 1890 had demonstrated the practicality of electric traction on London's Underground railways which at this time were principally steam driven. In 1898 Yerkes had bought a large interest in London's District Railway which was in need of huge investment.3 With his wealth of experience in Chicago, he believed that electrification and modern construction methods would substantially improve the line's performance and profitability. Yerkes was also interested in acquiring shares in the proposed deep level Charing Cross, Euston and Hampstead Railway Company (CCE & HR – now part of the Charing Cross branch of the Northern line). In 1900 he paid £100,000 to the company and became its Chairman. By March 1901 Yerkes had obtained control of the District Line forming the Metropolitan District Electric Traction Company (MDET). In July of that year, he was able to raise £1 million to invest in the new company, most of it raised in the United States. The MDET acquired control of the CCE&HR together with the Brompton and Piccadilly Circus Railway Company in September 1901.

    As part of the latter acquisition, the MDET obtained the rights to construct a power station at Lots Road – first proposed in 1897 as a part of the expansion plans of the Brompton and Piccadilly Circus Railway Company – which had obtained parliamentary approval for the South Kensington to Piccadilly Line, including provision for the power station. A plan of November 1901 (Figure 1) shows the ground plan of the proposed power station superimposed on the then site plan. Construction commenced in 1902.


    In March 1902 the MDET acquired the incomplete Baker Street and Waterloo Line (now part of the Bakerloo Line). To raise further capital Yerkes created a syndicate backed by the financier Sir Edgar Speyer (1862–1932) to issue shares in a new company the Underground Electric Railways of London (UERL) later known as the Underground Group. In 1902 the UERL acquired London United Tramways (the effective equivalent of Chicago's street railways).

    As well as these business acquisitions, mergers and creations, Yerkes had to drive through his proposals for the electrification of the railway systems which had undergone part electrification from 1890, in particular convincing his backers that his system was appropriate.


    The construction of Lots Road power station in three short years (1902–1905) from driving the foundations to first operational status in June 1905 (full operational status was achieved in May 1906), owed much to Yerkes' impatient energy, which had also marked his approach to railway construction in Chicago. Ironically Yerkes died in New York on 29 December 1905 at the age of 68, before his vision for the London Underground, including Lots Road power station, was fully completed. His great opponent, Mayor Carter Harrison Jnr, of Chicago said of him,

    Radical frame, conventional cladding: building the power station

    The overall design of the Power Station is thought to have been the work of the American engineer James Russell Chapman (1850-1934), who was General Manager and Chief Engineer of the UERL and is believed to have worked with Yerkes on the Union Loop Railway in Chicago. In June 1901 Chapman invited tenders for construction of the power station and for the supply and installation of its plant.

    Construction had commenced on the Lots Road site by March 1902 with the driving of 220 concrete piers to a depth of 10.60m into the London clay (Figure 2) to form a secure base for the steel frame of the building, erection of which commenced in May 1903, and was completed in nine months. The whole superstructure was completed in twelve months, by Mayo and Hailey of the Fulham Steel Works Company Limited who were subcontracted by the British Westinghouse Electric and Manufacturing Company, for which James Stewart and Company acted as building managers.5 At the time, an astonishing programme for a building of this scale.

    The then innovative steel frame technology appears to have been determined by Yerkes and Champion's experience in America, and particularly Chicago where the use of steel frames in large scale industrial and commercial buildings was significantly in advance of contemporary UK practice.

    The technological conservatism of UK building practice compelled Yerkes and Chapman to source the detailed design of the 5,800 ton steel frame of the power station from the firm of Hein and Lehmann and Co of Düsseldorf, contemporary German experience in this material being also well in advance of British contractors. The Lots Road contract drawings were dimensioned in metric (millimetres) with German annotation specifying all dimensions and jointing. Consequently a full set of translations had to be provided to the UK main contractor, Mayo and Hailey.


    Systemised mechanised construction methodologies were employed including pneumatic riveting and the use of a portable electric crane.

    The lack of familiarity within UK building practice of large scale steel frame construction extended even to the need to recruit significant numbers of German steel erectors to work on the project. These were sub-contracted to Mayo and Hailey. The precise origin of the steelwork itself remains unclear, Mayo and Hailey and Germany are both quoted by different sources as suppliers for the steelwork.6,7 The scale of the building and observation on site of the differential deterioration in the steelwork within the structure may indicate that both were in fact used.

    As built and today, the main power station comprised two principal elements, a tall (42.42m) boiler house (138m long by 30m wide), encompassing four chimneys (83.33m high), just north of the Chelsea Creek and to its north a lower (36.07m high) turbine hall (138m long by 22.8m wide) fronting onto Lots Road, the whole forming one building complex (Figure 3: north and east elevation, Figure. 4: south elevation, Figure 5: east elevation, Figure. 6: west elevation).

    While the steel frame of the power station was wholly unconventional by contemporary UK standards, the external cladding of the structure in brick and terracotta was entirely in keeping with Edwardian taste. The roof was of glass and concrete.


    Erection of the cladding commenced in June 1903, and by December of that year it was well advanced. While it is possible that the design of the cladding originated with Leslie Green (1875–1908) who was appointed architect to the UERL in 1903, and whose designs for London Underground Stations are superficially similar, the documentary sources provide no corroborative evidence. More probably the design was produced 'in house' by Mayo and Hailey. A drawing showing 'the details of the Terracotta and Brickwork' and recorded as revised on 4 April 1903 is directly attributable to the firm. Certainly the external envelope to the power station is safe and traditional and possesses nothing of the innovative flair of the internal steel frame.

    It is clear that the UERL had no illusions as to the purpose of the power station, their own promotional literature of 1904 stating that, 'In general details the building will be considered as a factory for the production of a commodity and there will be no ornamental features'.8

    Powering the Underground

    By May 1906 when it became fully operational the power station was effectively a vast machine encased in a steel and brick skin. It functioned on three levels, firstly coal fuel was converted into energy through combustion in boilers that produced high pressure steam. Secondly, the steam was passed through a turbine to convert it from heat to mechanical energy, and third the energy generated by the steam turning the turbines was converted by the alternators into electrical power.

    As built, the station was powered by 64 Babcock and Wilcox WIF land type boilers burning 700 tonnes of coal per day. The boilers were arranged on two floors supported directly on the steel framework of the building with space for the addition of a further 16 units. The boilers were arranged in two facing rows on each floor with economisers behind. Eight boilers were grouped to supply steam to each turbine.


    The original turbines ordered were four each from the Westinghouse Electric manufacturing company of Pittsburgh and from the British Westinghouse Company. The machines comprised eight turbo-alternators, each having a standard output of 5,500 kW and operating at 1,000 rpm to give a frequency of 33.3 Hz.

    However, the Westinghouse machinery proved wholly unreliable, even during testing within Yerkes' lifetime, ultimately resulting in legal action between the UERL and Westinghouse. Between 1909 and 1910 the original turbines were replaced with new models supplied by C. A. Parsons and Co of Newcastle upon Tyne.

    In 1915 a new 15,000 kW turbo-alternator from C. A. Parsons was bought into service at Lots Road to supply the City and South London Railway (C&SLR) taken over by the UERL Co in 1913. Two further such units were installed by 1925. In 1921 four new boilers were installed in the space left in 1905 for future development. These Babcock and Wilcox CTM Marine Pattern units were installed on the lower floor of the boiler house with induced draught fans and economisers on the upper floor. Four further boilers of the CTM type were added by 1925.


    By January of 1925, the Power Station was reaching the end of its 'design life' and it was decided to replace all the existing plant. A programme of reconstruction was implemented from 1927 to the plans of Merz and McLellan which involved new plant accommodation at the west end of the boiler house and a new control room over the office range at the east end of the turbine hall and boiler house (part). The old boilers were decommissioned in groups of eight, four on each floor with each group of eight old boilers being replaced by four new boilers. Four additional boilers were added inside a temporary steel frame extension at the west end of the boiler house with two short steel chimneys. On completion of this programme in 1932, the station is thought to have had 40 new boilers and 10 new turbine/alternator sets, increasing capacity to 105,000 kW. This compares with the c.44,000 kW capacity of the original Westinghouse machinery in 1906.

    This major programme of modernisation was described as 'an admirable attempt to make a modern efficient plant of station, a quarter of century in Age' by the Electrical Times, in an article which neatly summarised the process flow within the building.9


    After 1932 little work was done to the power station for three decades. Early in World War II the control room roof was reinforced in concrete in an attempt to bomb proof the power station and the glazing on the main elevations was bricked up. Minor bomb damage occurred at the west end of the boiler house, demolishing the upper part of the gable end.

    Following World War II one turbine/alternator set and eight boilers were decommissioned leaving 32 boilers and 9 turbine/alternator sets. However, improvements to the switchgear meant that total capacity was now 168,750 kW.

    In 1960 the decision was taken to modernise the power station again and work commenced in 1963. Internally the station was effectively cut in half from north to south with the east end of the boiler house and turbine hall effectively stripped of plant and abandoned. The slightly larger western ends of these buildings were also stripped of their plant with the original internal supporting steelwork also being removed. A new steel frame was inserted and six new oil fired boilers and six new turbo/alternator sets were installed. The first new turbine and boiler were commissioned in July 1965. As part of the work the north east and north-west chimneys were reduced to below roof level and capped with concrete, while the upper parts of the south west and south east chimneys were rebuilt (c.1967). The fenestration of the Lots Road elevation and the west elevation of the turbine hall was crudely restored as part of this refurbishment. However, the temporary blocking of the Chelsea Creek fenestration was replaced with clumsy brickwork permanently blocking the windows and encapsulating the principal steelwork of this elevation (Figure 7). The conversion was complete by 1969.


    The oil crisis of the 1970s and the availability of North Sea gas led to the conversion of the power station to gas fuel in 1977. By the 1980s the cost of generating power at Lots Road was in excess of simply purchasing power directly from the National Grid and the power station's role became that of a back-up power source in the event of failure of the main supply. The station eventually closed in 2001 after 96 years of service.

    Lots Road in popular culture

    It is perhaps hardly surprising that a building which has formed such a highly prominent London landmark for over 100 years should have featured in popular culture. The Power Station appears in the final chase scenes of Antony Asquith's 1928 film 'Underground', is briefly described in the 1961 John Le Carré novel Call for the Dead10 and was the subject of an epic poem by John Birtwhistle11. 'Ziggurat mass of bricks a terraced mountain driving the City Undergrounds down cool-seeming rails ...'

    In The Bible According to Spike Milligan – Old Testament12 it was proposed that '[...] darkness was upon the face of the deep; this was due to a malfunction at the Lots Road Power Station' – a statement reflecting a common misconception that the power station supplied the National Grid.

    Decommissioning, decontamination, demolition and building recording

    After closure in 2001 it was recognised that in order to secure the future of the main power station building conversion was the only option, and following purchase of the site by Circadian Ltd in 2004, a management agreement was drawn up (10 February 2005) between them and HBMC (now Historic England) to set the scope of the extent of historic features to be retained and those elements which it was considered could be demolished and removed. Subsequently, conversion of the power station received planning consent from the Royal Borough of Kensington and Chelsea. Where demolition was proposed a detailed programme of historic building recording was implemented in advance of and in conjunction with the demolition works.

    The building recording, which extended to all of the buildings on the site was carried out by Wessex Archaeology, with the assistance of Brown and Mason, and Watermans13, latterly under the direction of CgMs Consulting. Between 2007 and 2010 all the ancillary buildings of the power station complex were demolished, together with the power station offices and control room. Within the main power station building a programme of plant removal and decontamination was carried out over the same period; the removal of asbestos taking eighteen months and the soft strip and dismantling of plant three months each. The concrete lining of the remaining power station bunkers was broken out and the underlying steelwork exposed.

    As this work advanced it became apparent that much of the steelwork, particularly in the upper parts of the building, had severely corroded and in places had perished entirely. This may have resulted from differential corrosion reflecting variations in the quality of the original steel, though exposure to chemical corrosion and the age of the building are also likely to have been factors. Consequent on this was a decision to remove the remaining bunker end plates which were in a poor state of preservation.

    Conversion and conservation

    The main power station building is to be converted for mixed use purposes with residential predominating. The conversion will include retention of both intact and both truncated chimneys. As part of the conversion the fenestration of the Chelsea Creek (Figure 8: Proposed Chelsea Creek elevation) and Lots Road frontages will be restored to match closely that of 1905 as will that of the east end and west ends of the turbine hall. The heavily mutilated east and west ends of the boiler house will have new, matching fenestration installed. Brickwork and terracotta on the four elevations will be restored, repaired or replaced (to match) as necessary. Within the power station two sets of the original steel supporting columns have been retained around the eastern chimneys up to and including the massive W frames that formerly supported the coal bunkers. This area will form a focal point within the new development and will include an interpretative area on the history of the power station as the power source of the London Underground.


    The conversion and conservation of a vast industrial structure such as Lots Road Power Station is no easy undertaking and it requires developers, planning authorities and heritage advisors to work together in a spirit of co-operation. When a building has exceeded its design life by eighty years, with minimal, and often unsympathetic repairs and alterations to the retained structure there will often be a need for the revision of proposals as new structural information emerges. Where change is necessary it must be achieved sympathetically and with a full understanding of the significance of the original structure.

    The author

    Duncan Hawkins BA (Hons), MSc, FSA, MCIfA is a company director and archaeological and heritage consultant.

    Notes and references


    2. Op. cit.

    3. 'Yerkes, Charles Tyson'.


    5. Clarke, J, 2014, Early Structural Steel in London Buildings. A Discreet Revolution. English Heritage p 320

    6. '"The Underground" Electricity Power Station at Chelsea'. The Builders' Journal and Architectural Record, 15 February 1905

    7. 'The Great London Power Station'. Scientific American, 17 December 1904

    8. Underground Electric Railways Company of London Ltd; 1904 outline description of the Chelsea Generating Station

    9. 'Lots Road reconditioned'. Electrical Times, 3 April 1930

    10. Le Carré, J, 1961. Call for the Dead. Pocket Books, New York, USA, p 27

    11. Birtwhistle, J. 1972. 'The Conversion to oil of the Lots Road London Transport Power Station', Anvil Press Poetry, California, USA

    12. Milligan, S. 1993. The Bible according to Spike Milligan, Old Testament. Penguin Books, London, pp 1-2

    13. 'Lots Road Power Station, London, SW10'. Historic Building Record, Site Code LP004, Wessex Archaeology, September 2009. Unpublished report

    Other sources consulted

  • Burgess, J M, Ninety Years of Power: A History of Lots Road Generating Station, London Underground 1905–1995
  • Chelsea Generating Station
    © GLIAS, 2016