Boris Johnson has launched a new £5 billion housing construction scheme for London.The mayor's office is to work with the Homes and Communities Agency to build new homes over the next three years."By enabling ordinary Londoners to move from being subsidisers to being investors in new homes, we will provide timely support to a struggling development sector and can expect a return on our investment in years to come, Mr Johnson said.As part of the scheme, the Greater London Authority is to resurrect earlier developments, buy-up unsold homes for affordable housing, use public sector land for new schemes and subsidise rent and new rent-to-buy initiatives.Mr Johnson hopes the strategy will tackle the historic problems of affordability, homelessness and overcrowding.Property prices in the capital have rocketed in the last ten years. However, some regions have a noticeable premium over others and most have suffered recent falls.Land Registry figures reveal on average London prices increased by only 1.4 per cent in the last year.