I've lived here about 8 years, and it's become much cleaner in that time.
I put it down to the new mayor, Ken Livingstone.
There's an interesting story there - he was also the Mayor of London about 25 years ago, a powerful position similar to the mayor of NYC.
He was very left wing, with politics about things like disabilty issues, gay and lesbian equality etc about 20 years ahead of his time. The media had a field day slamming him, but I went back and read some of these stories the other day, and the proposals certainly look a lot more reasonable in 2006. Shame they didn't fit 1981 too well.
He had a major battle with Maggie Thatcher's government, which was very right wing. Ken Livingstone's massive HQ was opposite the Houses of Parliament over the river, and he put up huge banners slagging off the government, listing what he felt was the real unemployment figures as opposed to the government's fiddled figures.
Maggie Thatcher responded by abolishing his postion, and abolishing the entire greater London authority, so that there was no longer anyone responsible for london as a whole. Each borough had its own local council and that was it. Kinda like each NYC borough, Queens, Bronx etc doing everything independently with no-one to co-ordinate them.
London still had a mayor, but it was some token old git who does nothing except wear gold chains once a year and stand in a horse and carriage at the New Year's Day Parade.
Fast forward 25 years ....
Our new great white hope, Tony Blair, wants be seen as saving the world, so he tries to solve the problem of Irish terrorism by setting up a local government in North Ireland.
Consquently he's forced against his will to agree to local government in London (and a few other places) so reluctantly agrees to set up a London authority and mayor with real powers.
Ken Livingstone promptly stands again for election (he is part of Tony Blair's Labour political party) despite Tony Blair telling him to piss off and not think about standing again.
Massive arguements ensue, Tony Blair throws him out of the Labour party, everyone slags off Labour's offical candidate for Mayor, several of which resign in quick sucession, and Ken wins the election by a mile.
Tony Blair backs down and readmits him to the Labour Party, cos in London he's more popular than Labour party itself (at that time).
Ever since, Tony has been doing everything possible to wreck Ken's efforts to resurrect London - dirty tricks, secret press briefings against Ken, offical lack of co-operation, denial of Ken's independent fundraising initatives, pressing ahead with dodgy Government-sponsored PPI finance deals etc.
I have to say, I think London's become much cleaner since Ken came back (like Apple under Steve Jobs

) London transport has really improved, there's a bus every 5 minutes now, some nice new buildings, recycling rate has gone up, won the olympics etc.
While Ken's original politics were 20 years ahead of his time, now the world has moved on; he's also progressed in some ways, like becoming very green, but he's also remained stuck in some ways. There's been plenty of criticism of him and he's made some major blunders, but overall he's done a good job against some heavy opposition.