The independent candidate will no longer run in the next London mayoral election which will now take place in 2021 due to coronavirus.
Mayoral and local elections will be postponed for a year due to the coronavirus outbreak, Boris Johnson has said.
The Labour incumbent has launched his bid for a second term as London Mayor, citing housing, violent crime and air quality as priorities.
The London mayoral candidate has promised stop and search as well as a "second chance fund" to make streets safer in the capital.
Dave Hill spoke to Julia after Zac Goldsmith lost the Richmond Park by-election to the Liberal Democrats.
Steve Hilton explains why the Tory's bid for London mayor was poorly conceived
The Respect Party's candidate for mayor chats to Julia Hartley-Brewer ahead of the election
The pair's twitter argument was replayed on air on Monday morning
UKIP Mayoral candidate joined Julia Hartley-Brewer in the studio
The Green Party's leading candidate has her say ahead of the May 5 election
Lib Dem candidate attacks her rivals and frontrunners for the post
Richmond Park MP dismisses the idea he won't be able to represent the capital because of his upbringing
Labour MP for Tooting responds to his rivals claims he would be a 'disaster' for the city