section of the District's deep-level tube from South Kensington to Mansion house was dropped from plans. In April 1902, the Underground Electric Railways Company of London (UERL) was established, with Yerkes as chairman, to control these companies and manage the planned works. On 8 June 1902, the UERL took over the Traction Company and paid off the company's shareholders with cash and UERL shares. The UERL built a large power station that would be capable of providing power for the District lines and the underground lines planned. Work began in 1902 at Lots Road, by Chelsea Creek and in February 1905 Lots Road Power Station began generating electricity at 11 kV Hz, conveyed by high voltage cables to substations that converted this to approximately 550V DC. While the power station was being built, the District electrified the Ealing to Harrow line that was not yet open. It was equipped with automatic signalling using track circuits and pneumatic semaphore signals, and trials were run with two seven car trains. In August 1903, an order was placed for 420 cars and a new maintenance depot was built west of Mill Hill Park (now Acton Town). After the trials, the line to South Harrow opened in June 1903, from 23 June with a shuttle to Park Royal & Twyford Abbey (now Park Royal) for that year's Royal Agricultural Show. The rest of the line to South Harrow opened the following week on 28 June, with stations at North Ealing, Park Royal & Twyford Abbey, Perivale-Alperton (now Alperton), Sudbury Town, Sudbury Hill and South Harrow. Electric services Electric services began on 13 June 1905 between Hounslow and South Acton, using the line from Mill Hill Park to South Acton for a passenger service for the first time. Hounslow Town station was reopened, trains reversing at the station before continuing to Hounslow Barracks using a new single track curve. On 1 July 1905 electric trains began running from Ealing to Whitechapel, and on the same day the Metropolitan and District railways both introduced electric units on the inner circle. However, a Metropolitan multiple unit overturned the positive current rail on the District Railway, and investigation showed an incompatibility between the way the shoe-gear was mounted on the Met trains and the District Railway track, and the Met trains were withdrawn from the District lines. After modification the Met returned and electric trains took over on