Instead of walking through the door with him, his girlfriend Carrie Symonds, former head of communications for his Conservative Party, stood nearby with his staff – a sign of a colourful private life that arguably represents modern Britain better than the traditional picture.
For decades, the new prime minister has been expected to take part in the somewhat contrived set-piece of giving a cheery wave to the massed ranks of the media on crossing the threshold of No.10 for the first time – with a spouse, and perhaps their children.
But Johnson, 55, and his wife Marina Wheeler, who have four children together, announced in September that they had separated and would divorce after 25 years.
This was twice the length of the average marriage in England and Wales, where there are 64 divorces each year for every 100 marriages.
The highly visible role of Britain’s national leaders has generally meant they are held, however anachronistically, to a somewhat different standard.