Shared ownership was created with a clear purpose: to help working households who are priced out of the open market but who can afford stable monthly housing costs, to buy a home. In London, that has always meant key workers - the teachers, nurses, police officers and public servants who keep the city functioning but earn on public-sector pay scales.

Buyers purchase a share of a home - typically between 25 and 50 per cent - and pay a regulated rent on the remaining share, owned by a housing association. This lowers the deposit required, reduces the size of the mortgags and keeps monthly costs affordable. Over time, buyers can increase their share as their circumstances allow, providing a stable route into full homeownership.