In what may be Cameron’s most explosive allegation yet, he effectively accused Boris Johnson of mounting a racist election campaign by focusing on Turkey and its possible accession to the EU.

“It didn’t take long to figure out Leave’s obsession,” he writes. “Why focus on a country that wasn’t an EU member?

“The answer was that it was a Muslim country, which piqued fears about Islamism, mass migration and the transformation of communities. It was blatant.”

Then Cameron echoes the explicitly racist Conservative campaign slogan used in Smethwick in 1964: “They might as well have said: ‘If you want a Muslim for a neighbour, vote “remain”.’”