 New branches to Uxbridge , Watford and Stanmore were built , and from 1915 the extremely effective Metro @-@ land advertising campaign began , promoting the lightly developed areas along the MR 's routes as ideal for commuting to London . Watkin 's expansionist schemes had led to the acquisition of huge tracts of near @-@ worthless land in the Buckinghamshire countryside around the MR 's routes , as the MR had tried to take control of as much land as possible along every possible route between London and Manchester . With the GCR complete it was no longer necessary for the MR to keep these lands clear for potential railway use , and Selbie began development on a massive scale . By 1939 over 4 @,@ 600 houses had been built by the MR alone , and entire new towns had grown around the MR 's stations between Harrow and Aylesbury . This development not only generated huge amounts of money from property development , but vastly increased use of the railway for passenger and goods traffic . The MR 's Baker Street terminus was also redeveloped and a block of 180 luxury apartments known as Chiltern Court was built above the station . With the profits generated , the line was further electrified as far as Rickmansworth . Again , the Chesham branch was not electrified and remained operated by steam locomotives ; the electric locomotives would be uncoupled from their trains at Rickmansworth and a steam locomotive would haul the train to Chesham . By this time , the steam sections of the route were generally worked by the powerful Metropolitan Railway H Class engines , capable of speeds of up to 75 miles per hour ( 121 km / h ) . 
