London's housing situation and the election trail
A record number of affordable homes were completed in London last year.
But although it was the highest numerically, it represented just 28% of all homes completed in the capital - the lowest rate in a decade.
Latest government figures show there were 17,914 completions in the year to April 2015, compared to 8,114 affordable homes finished in 2013, and 8,709 in 2014.
Numerically, 2015 marked a sharp recovery.
But when London's population is growing by about 100,000 annually, this acute housing shortage has made the issue more potent than in previous elections.
More houses needed
More than 9,500 of the homes finished last year were for what is now called "affordable rent" - meaning occupants are charged up to 80% of private rental levels in the area.
Just over 3,000 homes were available at "social rent" typically set at 40-50% of private rent levels and what is traditionally charged for council housing.
And more than 5,260 were provided for people who want to part-rent or part-buy.
Case study: Richard Hill, aged 28
Richard lives with his parents in Brentwood, Essex and works at the University of Roehampton. He earns £30,000 a year and says he can't afford to buy in London and won't be able to at least for the next five years. Commuting costs him £4,000 a year.
"I could find a room in a house-share but then I would be forever trapped in a 'generation rent' market. As soon as you rent it makes it near impossible to save for a deposit. I am saving now, doing things like bringing my own packed lunch into work.
"It's quite depressing. Every little helps but only saving £50 a week doesn't make a very substantial dent.
"It's a long commute to work, a good hour and a half and it's expensive. But it's the only option at the moment. It's either grin and bear paying the extortionate rent prices in London or commute in and pay the extortionate commuting fees.
"My parents don't want me there. I don't want to be there. But it's purely because I don't have any choice."
But the number of completions will have to keep on rising to more than 18,000 next year if the mayor is to match the 53,000 affordable homes built in his first term, mainly under Labour's National Affordable Housing Programme.
And more than 12,000 new affordable homes need to be finished this financial year if he is to meet his own target of 100,000 over eight years and the conclusion of his second mayoral term in 2016.
The Conservatives pushed housing to the centre of their campaign last week - promising to extend the right-to-buy policy to an estimated 1.3 million housing association tenants in the UK.
The plan is opposed by Labour, the Liberal Democrats and the Greens.
The Tories have also pledged:
•200,000 homes for first-time buyers aged under 40, at 20% discount
•New Help to Buy ISAs for first-time buyers
Labour say they will
• Exempt first-time buyers from stamp duty when buying homes for less than £300,000
•Get 200,000 homes built a year by 2020
•Guarantee three-year tenancy agreements in the private sector and a "ceiling" on rent increases
•Prioritise local first-time buyers in new housing areas
The Liberal Democrats want to:
•Increase house-building to 300,000 a year
•Set in motion at least 10 new Garden Cities
•Create 30,000 Rent to Own homes a year by 2020
The Greens claim they would:
•Build 500,000 social rental homes by 2020
•Abolish the right to buy council homes
UKIP aim to
•Prioritise social housing for people with parents born locally
•Hold referendums on major planning decisions