The next Mayor of London should turn South London orange — by incorporating London’s local and suburban main line services into the successful Overground network. This would hugely improve London transport and boost jobs, housing and regeneration.

The Underground largely serves London north of the Thames and is managed by TfL. Most of south London, despite 227 stations serving five million people, depends on suburban services which play second fiddle to long-distance rail firms, and which are underdeveloped and poorly managed.

Much of south London suffers from skeleton services through bleak stations barely touched for a century. It’s a key part of London’s north/south divide.

The Overground network, opened over the past decade, shows how different it could be. The orbital line, extending from Islington and Hackney to Peckham and Clapham, was the result of visionary reform begun under Ken Livingstone. It took existing underused stations and services, upgrading, extending and linking them to create an integrated metro service, under TfL control, as with the Tube.

Passenger journeys on the orange network have increased by 450 per cent since Overground’s launch, compared with 50 per cent on south-eastern suburban rail lines. Passenger satisfaction ratings have risen from 57 to 92 per cent, thanks to better, more frequent trains, new routes, brighter stations and improved reliability. Capital investment made this possible but the change was as much about TfL management overcoming complex operational issues by focusing on the “orange vision” of a transformed metro system.

Operating subsidies on the Overground have been reduced by the passenger surge, while long-distance and freight services sharing the orange lines have not suffered. This orange vision now needs to sweep across the rest of our suburban rail network.

As a first step, management of the south London suburban lines should transfer to the Overground when the various southern rail franchises come up for renewal over the next seven years. There should be an immediate “orange transfer” of the south-western suburban lines through Wimbledon — including the major commuter stations in Kingston, Surbiton and Chessington — to accelerate progress on Crossrail 2.

When completed, Crossrail 2 will route south-western suburban services that currently go to and from Waterloo into a new tunnel at Wimbledon, taking them straight to and from Clapham Junction, central London, Haringey, Hackney and major regeneration zones in north-east London. Crossrail 2 needs to proceed as rapidly and boldly as possible, at the heart of an extended Overground.

With each transfer, the Overground’s service standards should be applied, including all-day station staffing, public information systems, Oyster fare zones and improved lighting and maintenance. Extra services would follow, alongside the building of new housing, from which much of the cost could be recouped.

Within 15 years — when Crossrail 2 could be open — this extension of the Overground would have brought about another orange revolution. The orange network would be as extensive as today’s Underground network — one system serving the whole of London for the first time since building the Underground began more than 150 years ago.

Andrew Adonis is a former Transport Secretary.