Today's fast-paced developments mean Cameron's swansong to his premiership is brutally cut short and his wife Samantha and three children Nancy, Arthur and Florence will have to start packing their bags tonight to make way for May and her husband Philip on Wednesday.
His six-year tenure as Prime Minister was expected to end on September 9 and he was looking forward to final farewell tours to Africa later this month and China in September for the G20.
The trip to China would have allowed Cameron to bid farewell to many of his international colleagues.
Britain's constitution allows for a quick turnaround and now May's election as Conservative Party leader is confirmed, the machinery of government will jump into top gear to hand over power.
Tomorrow Cameron will chair his last Cabinet meeting and then Wednesday's Prime Minister's Questions will allow him to bid farewell from the frontbench and his colleagues to pay tribute to him in the Commons.
But he is unlikely to receive the same kind of reception MPs gave Tony Blair when he quit as PM in 2007, with MPs clapping him out of the Commons in a break of tradition.
He will then take the short journey to Buckingham Palace to submit his resignation to the Queen, before May makes the same journey to inform the Queen she is forming a new government.
The new Prime Minister will spend this week appointing her new government, with big Cabinet roles expected to be handed to her close allies and Brexit champions Chris Grayling and former Defence Secretary Liam Fox.
Boris Johnson and Leadsom are also expected to be handed Cabinet positions, while Chancellor George Osborne and Foreign Secretary Philip Hammond could swap jobs.
Cameron emerged from Downing Street this afternoon to confirm the timetable for his departure and paid tribute to his successor.
He said: "I'm delighted that we're not going to have a prolonged Conservative leadership election campaign.
"I think Andrea Leadsom has made absolutely the right decision to stand aside and it's clear Theresa May has the overwhelming support of the Conservative parliamentary party.
"I'm also delighted that Theresa May will be the next Prime Minister; she is strong, she is competent, she is more than able to provide the leadership that our country is going to need in the years ahead and she will have my full support.
"Obviously with these changes we don't need to have a prolonged period of transition and so tomorrow I will chair my last Cabinet meeting, on Wednesday I will attend the House of Commons for Prime Minister's Questions and then after that I expect to go to the Palace and offer my resignation, so we'll have a new prime minister in that building behind me by Wednesday evening."
May's Cabinet is likely to meet for the first time next Tuesday before the new Prime Minister makes her PMQ's debut on July 20, the day before the House of Commons rises for the summer.
The Cameron family actually lives in the flat above No 11 Downing Street, which is larger, while the Osbornes live over No 10.
But if George Osborne is moved on from the Treasury under the new administration, removal teams will be hard at work in Downing Street clearing both flats.
The Tory leadership contest was cut short today after Andrea Leadsom
announced she was pulling out of the race
