Sir James Cleverly has resigned from the shadow cabinet with immediate effect to launch a bid to become the next Mayor of London.

The former Home Secretary and Foreign Secretary stepped down from his role as Shadow Housing Minister under Conservative leader Kemi Badenoch. In an op-ed, Sir James explained that he made the decision to clarify his future ahead of the party's annual conference in October, arguing that running an effective campaign requires his full attention.

"Serving there has been a privilege, and I know there will continue to be strong voices around that table," he wrote regarding his departure from the shadow cabinet. "But to run the most effective campaign possible, I must be free to speak about every aspect of London’s future and concentrate fully on winning this race."

A source close to Mrs Badenoch said the Conservative leader was "gutted" to lose him from her top team, but noted she is "delighted that someone of his calibre wants to put himself forward to be Conservative nominee for mayor of London." The party leader cannot officially endorse his bid at this stage, as Sir James must still formally win the nomination through the party's selection process.

The 56-year-old MP for Braintree brings previous City Hall experience to the contest. Born and raised in Lewisham, south London, he served as a London Assembly member for Bexley and Bromley until 2016. He was first elected to Parliament for Braintree in 2015 and subsequently held senior government posts, serving as Foreign Secretary under Liz Truss and Home Secretary under Rishi Sunak.

Taking direct aim at current mayor Sadiq Khan, Sir James argued that the capital's reputation has suffered in recent years. "It’s the visible things that are damaging London’s reputation," he said, pointing to "the impression that the mayor has given up on policing the streets" alongside "the constant ratcheting up of tax and regulation." He added: "The way you deal with bad news, even if it’s unfair, is to put better news out there. Khan has spectacularly failed to do that."

Sir James also argued that regaining ground in the capital is critical for the wider Conservative Party, rejecting suggestions that the city is permanently lost to Labour. "Our route to getting Kemi in No10 has got to be through success in London," he said, describing the capital as the "philosophical heart of the Conservative Party" while adding that Mrs Badenoch is "getting great cut through" with the public.

The mayoral field is already starting to take shape. Reform UK has confirmed Laila Cunningham, a former Conservative councillor in Westminster who leads the party's London branch, as its candidate for the 2028 election following an announcement earlier this year by Nigel Farage.

Questions also remain over whether Sir Sadiq Khan, who was elevated to the peerage by Sir Keir Starmer, will run again. Sir Sadiq has indicated he will make a final decision next year after speaking with his family. While he noted that his "tank is full" and he is "still fizzing with ideas," he also remarked that he is "not sure it's good for one person to be in charge for too long," despite pointing to polls suggesting he would win a fourth term.

What we do not know yet is who else will step forward to challenge Sir James for the Conservative nomination, or the exact timetable the party will set for members to choose their candidate.

I'll be following this one closely as the selection contest gets under way — check back for updates.