Comment: Lofty targets, but a challenge to achieve them

At first glance it looks as if nothing much has changed: Boris, like Ken, wants to help London's growth. He uses the same predictions of population (about eight million by 2016) and wants to keep growth inside the Green Belt, which means densification, or more people living per square mile.

The new mayor, like the old, sings the praises of diversity, sustainability, "vibrancy", inspiring new architecture, public space, trees, the Thames, affordable housing and Crossrail. He even "supports tall buildings". He sees opportunity in the development of east London and the Thames Gateway.

All of this could have come straight from the writings of Mr Livingstone's architectural adviser Lord Rogers but there are differences.

The first is that Boris wants to work with the boroughs, and leave as many decisions as possible to them, whereas Ken was threatening to use his enhanced powers to subjugate them. The second is that Boris has abandoned Ken's target of making half of all new housing affordable, on the grounds that it was never attainable.

Instead, he wants to achieve 50,000 new affordable houses in three years.

In a stagnant property market, this will have to come from central government funding through its Homes and Communities Agency.

He says that tall buildings have to be in "appropriate locations". In theory Ken said this too but in practice he regarded almost anywhere as appropriate: Boris will take a more restricted view. He singles out London's World Heritage Sites as needing particular protection, meaning he will be less favourable to towers in Waterloo, Vauxhall and Battersea which would eclipse views of the Palace of Westminster.

Boris also talks up the joys of suburbia, of protecting back gardens and helping outer London. He proposes an "Outer London Commission", and policies to support growth in the suburbs. This is true to his campaign as a mayor for all of London. Mr Livingstone was seen as a Zone 1 mayor and Lord Rogers never seemed comfortable dealing with places outside the metropolitan centre.

So Mr Johnson is offering a softer, more civilised version of MrLivingstone's plan. He is promising to achieve those things, such as well-designed new neighbourhoods and good quality homes, which the last mayor also promised but which got left behind in the rush for growth.

The big question is how he achieves his lofty aims. The new document is for discussion only, and includes such vague promises as "a major seminar" on housing, at which Mr Johnson the columnist would surely scoff. It will take until 2012 to complete the overhaul of the London Plan, by which time a new mayor might be ready to take over, although some policies could take effect before then.

So the mayor's "direction of travel" cannot be faulted. Now he needs to show us how he is going to get there.