Londoners will be able to vote in American presidential-style primaries to choose Labour's next candidate for mayor.
Party members and people who register as Labour supporters can have their say.
The change announced today by Ed Miliband reduces the impact of trade unions on the selection of candidates.
The details now from our Political Correspondent Simon Harris
More top news
Muslim leaders condemned the "heinous and appalling" Westminster terror attack.
Travis Frain is recovering in hospital and has posted a photo to Twitter of Prince Charles by his bedside.
Acting Commissioner Craig Mackey led new policemen and women in paying their respects at a passing-out parade in Hendon, north-west London.