brownfield

That, however, was a brownfield site, rather than a city centre landmark.

The Balfron Tower was designed by Hungarian-born architect Ernő Goldfinger in 1963 and was built between 1965 and 1967 as part of the Brownfield Estate, an area of social housing.

The announcement marks a change in stance for Sir Sadiq, who has previously argued against releasing green belt land while there are still previously developed brownfield sites available.

London has a new target of building 88,000 new homes a year, but the current plan, which relies on building on brownfield sites, is delivering only around 40,000 a year.

While the mayor is expected to continue prioritising brownfield land, he is expected to tell his audience on Friday: "We have to be honest with Londoners that this alone will not be enough to meet our needs."