Boris v Ken again.

Boris and Ken - head to head during the last London mayoral election

Elections in Britain are essentially contests between parties. But that's less true of elections for London mayor.

Ken Livingstone, who has twice been elected mayor, has made a career out of disagreeing with the Labour Party while the man he lost to in 2008, Boris Johnson, often and loudly attacks Conservative policies.

Next year these two big political personalities will take each other on in the next contest for London Mayor. No doubt the Greens and Lib Dems will be playing up their chances but few doubt the winner will be Boris or Ken.

And although the campaign isn't officially under way, behind the scenes the planning has already started as Leala Padmanbhan reports: