Just musing... I think the next London Mayor is likely to be Labour.
Boris outperformed the Tories massively last time round and there is no-one sufficiently charismatic to replace him if Lord Coe doesn't stand (it seems he won't). The only way I can see of the Tories winning in London is if Ed Miliband wins the GE.
Sadiq Khan is out of the race. He won't condemn Ed Miliband (something the others, like Lammy, would be quite prepared to do) and he won't be able to escape the questions about whether he was driving whilst using a mobile phone.
I detest Diane Abbott's politics and hypocrisy but respect her political skills, she may have enough name recognition. I think Tessa Jowell would be the 'sensible' option with a reasonable amount of name recognition but she might just be too boring. I don't think any of Labour's London Assembly members have anything near the right profile.
Christian Wolmar - who? A trainspotter might be a good manager of TfL but not a mayor who needs to denomstrate character, visibility, vision and leadership. Lord Adonis fails for the same reason.