Starter's orders as Khan and Hall set out mayoral pitch

The starting gun has been fired on the race to be the next mayor of London - with Sadiq Khan and his main challenger trading blows and warnings that the Ulez row could play a key role Despite the Mayor being well ahead in a number of polls, well-informed activists believe a low turnout and changes in the voting system could leave "only 10,000 votes" between the Labour mayor and his Tory rival Susan Hall.

- Ross Lydall, Noah Vickers & Nicholas Cecil

Labour fears Mr Khan's big poll lead - two surveys in November put him on 50 per cent, compared with about 25 per cent for Ms Hall - could lead to complacency among supporters.

It has adopted a three-pronged strategy to secure him an historic third term, the Standard has been told: getting the core Labour vote out, convincing Green and Lib-Dem voters to "lend their vote", and discouraging Londoners from voting Conservative. But Ms Hall believes her campaign, which focuses on safer streets and ending the "war on drivers", is resonating with voters, especially in Tory outer London heartlands.