The speed with which Mr Johnson was ousted, a little more than two years after winning a landslide election, has taken the couple – who now have two young children – by surprise.
A source said the flat move had been timed to coincide with their family holiday to provide easier access for the removal firm – the same one used by Theresa May after she was forced out of power.
“We want to make the transition as smooth as possible. This is a convenient time to move some of the big stuff out,” the source said.
According to aides who have worked alongside Mr Johnson for years, he remains “in shock” at the “speed and brutality” of his ousting from Number 10.
One senior Downing Street adviser said Mr Johnson’s fury at his betrayal by Rishi Sunak, the former chancellor whose resignation sparked his downfall, has turned to pity as he watches him trail Liz Truss in the Tory leadership race.
Mr Johnson is unsure what he will do next, with the spectre of an investigation by the House of Commons privileges committee into whether he misled MPs over partygate hanging over him.
The committee’s findings could derail his plan to continue as an MP.
Mr and Mrs Johnson are spending a week in Greece, having been spotted by locals shopping in a supermarket in Nea Makri, a town to the east of Athens. Mr Johnson’s father owns a holiday home in mainland Greece, but the couple are not thought to be using the villa because it was already rented out to a British family.
A well-placed source said the Johnsons would spend the remaining weeks of his premiership at Chequers.
“He has already spent most of his time there since the resignation,” said the source. “I think Boris will probably spend the odd day in Downing Street, but I think they will mainly be at Chequers.
“After he leaves office, they need to sell the house in Camberwell first before they can buy a new home. He doesn’t have family money and he might lose his salary as an MP. He will take the stuff he paid for out of Downing Street but he won’t be taking the wallpaper.”