Britain's Prime Minister David Cameron returns to 10 Downing Street after making a statement in Westminster, London, July 11, 2016. [Photo/Agencies]

LONDON - British Prime Minister David Cameron appeared in high spirits when he appeared briefly outside his Downing Street office on Monday to outline this week's timetable for his resignation.

As he walked back towards the portico of his official residence, TV microphones picked him up humming contentedly and following up with a jaunty "right!" as he closed the familiar black door behind him.

He had just confirmed that he would offer his resignation to Queen Elizabeth on Wednesday afternoon and that his successor Theresa May would "be in that building behind me by Wednesday evening."

Cameron, who has been in Downing Street for six years, resigned last month after suffering the hardest political blow of his life when voters rejected his appeals to stay in the European Union.

But in recent days he has appeared more cheerful, appearing alongside his mother in the Royal Box at Wimbledon on Sunday to watch Briton Andy Murray win the men's singles tennis title and perhaps contemplating the prospect of a Summer holiday with his family - and without the media.

He had already announced he would not seek a third term and would stand down before the next national election, due in 2020.