Vote Leave campaign leader Boris Johnson leaves his home in London, Britain June 29, 2016.  [Photo/Agencies]

New UK Prime Minister Theresa May stunned the British political world by naming former rival Boris Johnson to the key post of Foreign Secretary only hours after she formally accepted Queen Elizabeth's invitation to form a government.

Former Chancellor of the Exchequer George Osborne, who served for six years alongside old school friend David Cameron, was told by May there was no new role for him in her government, and resigned.

Philip Hammond, who served as Foreign Secretary and Defence Secretary under Cameron, took over as Chancellor.

Cameron quit after Britons dramatically voted in favour of leaving the European Union in a June 23 referendum. Johnson, the flamboyant former Mayor of London who upset many senior Conservative Party politicians by opting to head the Leave campaign, had originally been tipped as a future prime minister.

But he was sensationally pushed out of the running to succeed Cameron when his campaign manager, Michael Gove, abruptly announced he was running himself. He withdrew and most expected him to vanish into political obscurity.

May also named a veteran Conservative Party legislator, David Davis, as Secretary of State in charge of negotiating the exit process from the EU. Amber Rudd, who has only been in the cabinet for a year, took over the Home Office rule, formerly held by May.

A former defence secretary, Liam Fox, was named to the new post of International Trade Secretary, and will be given the task of negotiating fresh bilateral deals, especially with China.