and were eventually cut back or ended while other, more radial services on the lines continued. Other semi-orbital routes fared little better. Throughout the 20th century London's railways operated on a radial model and the few remaining semi-orbital passenger routes withered, with the lines used mainly for freight services. The national railway network was privatised with radial franchises. Only the Circle line enjoyed success. Throughout the 20th century London expanded both in size and population and employment ceased to be as heavily concentrated in the centre. Many more people were travelling through central London by Underground and many of them were travelling in on one radial route only to travel out again on another. Congestion increased and additional Underground lines were built at great expense. The idea of reviving and expanding the semi-orbital routes to relieve some of the load on central London in a more cost-effective way than the building of new tube lines was considered, coalescing around the suggested name "Orbirail", but it won few friends in the National Rail network for commercial and operational reasons. The situation changed drastically with the creation of Transport for London as a single body with overall responsibility for transport in London. During Ken Livingstone's term as Mayor of London, TfL exploited the potential in the neglected peripheral rail routes and started to plan a complete orbital rail system by joining these routes together (albeit with no plan for a single fully orbital service). The new system was eventually launched as the London Overground, and work continues to complete the orbital route as more lines are added to the system. The eventual London Overground network will (by 2013) cover a route which bears a striking resemblance to the Outer Circle line with the East London line extension and South London Line being used to complete the loop. Political support for the principle of Orbirail continued after the change of leadership following the 2008 London mayoral election. During his election campaign, Boris Johnson published a transport manifesto which highlighted the problems associated with orbital journeys around London: R25 The R25 was a proposed railway orbital around the Zone 3 area of London. First proposed in the Mayor of London's £1.3 trillion London Infrastructure 2050 plan, the line would have used some existing Network Rail and London Overground lines, linked by stretches of new railway. Arguments for and against The manifesto noted that 64%