inner circle. A tender was announced for an electric system, and the largest European and American companies applied to win the tender. However, when the experts of the London Metro compared the design of the Ganz Works to the offers of the other large European and American competitors, they have found, that the newest type of AC traction technology of the Ganz Works is more reliable, cheaper and considered its technology as a "revolution in electric railway traction". In 1901 a Metropolitan and District joint committee recommended the Ganz three-phase AC system with overhead wires. Initially this was accepted by both parties, until the District found an investor, the American Charles Yerkes, to finance the upgrade. Yerkes raised £1 million (1901 pounds adjusted by inflation are £) and soon had control of the District Railway. His experiences in the United States led him to favour the classic traditional DC system similar to that in use on the City & South London Railway and Central London Railway. The Metropolitan Railway protested about the change of plan, but after arbitration by the Board of Trade the DC system was adopted. The Metropolitan electrified its new line from Harrow to Uxbridge and the route to the inner circle at Baker Street, using separate positive and negative conductor rails energised at 550–600 V. The District electrified its unopened line from Mill Hill Park (now Acton Town) to South Harrow and used this line to test its new trains and train drivers. Electric multiple units began running on the Metropolitan in January 1905 and by March all local services between Baker Street and Harrow were electric. Electric services began on the District Railway in June 1905 between Hounslow and South Acton. In July 1905 the District began running electric trains from Ealing to Whitechapel and on the same day the Met and the District both introduced electric units on the inner circle until later that day an incompatibility was found between the way the shoe-gear was mounted on the Met trains and the District track. The Met trains were withdrawn from the District lines and modified, full electric service starting on the circle line in September. In the same month, after withdrawing services over the un-electrified East London Railway and east of East Ham, the District were running electric services on all remaining routes. The GWR electrified the line between Paddington and Hammersmith and the