The Mayor of London is ploughing millions of pounds more into Peabody’s landmark housing scheme on the former Holloway Prison site to ensure that 70 per cent of the affordable homes there will be for social rent.

City Hall already loaned the housing association £42 million when it bought the site from the Ministry of Justice last year.

The extra money will be used to convert the homes that were going to be available at London affordable rent into social rent, which is set by a national formula and is the cheapest form of affordable housing.

While the two types of rent are often said to be similar, social rent is generally accepted to stay lower for longer and this is one of the changes that housing campaigners have been asking for.

Overall, the scheme will deliver 60pc genuinely affordable homes, with 42pc of the total homes on site now at social rent.

This comes following concerns Peabody was planning to water down a promise to provide 42pc social rent housing in the development.

Andy Bain, a housing campaigner from Islington Homes for All, told the Gazette: “It’s a small victory in that Peabody has been forced to go back to where the original agreement was, and the 42pc social housing that was originally planned.

“But there is so much public money that’s gone into funding this development that there should be a lot more social housing than that.”

The exact amount of funding depends on the final designs for the homes, but is expected to be about £10m.

Work is expected to start building the first homes on the site in 2022 and the development should be complete by 2025.

Tom Copley, deputy mayor for housing, said Londoners “desperately need” high-quality, socially-rented homes and this is a “vote of confidence in this vital project that will deliver housing the people of Islington can be proud of”.

The leader of Islington Council, Cllr Richard Watts, added: “The Holloway Prison site is one of enormous significance for Islington and it’s vital we use this once-in-a-generation opportunity to deliver as many genuinely affordable homes on this large site as possible.”

“We applaud the mayor’s commitment to tackling London’s housing crisis and welcome the additional funding.”

While restrictions set by central government limit the mayor’s ability to fund homes at social rent, Sadiq Khan has indicated that securing flexibility from government will be a priority for the next affordable homes programme, which starts next year.

Dick Mortimer, executive director for development at Peabody, said: “Peabody bought the Holloway Prison site with a clear commitment to provide as many affordable homes as possible.

“This reflects our social purpose and we’re delighted to be able to propose a development that will deliver nearly 1,000 new homes and 42pc social rent with the ongoing support of the mayor. The planning application is still to be submitted but we believe our scheme will result in a high-quality development that everyone can support.”