LONDON — Not the kind of headline you read everyday in Britain, but here it goes: "Boris Johnson admits he has six children."

You wonder: Why we didn’t know that? The answer is the British prime minister has dodged the question for years.

Various publications have gone with five, six or seven offspring. Seems simple, but not. The Guardian explained that Johnson has been “previously coy . . . about his notoriously complex family life.”

His biographers have fudged the issue. So did his Wikipedia entry. So has The Washington Post.

On Tuesday, speaking with NBC’s “Today” show from the sidelines of the United Nations General Assembly in New York, in a discussion about fatherhood, the thrice married Johnson was asked if he had six children — and he replied, rather quickly, “yes.”

The 57-year-old British leader has four grown children with second wife Marina Wheeler, a barrister, from whom he separated in 2018. And with his current wife, the former Conservative Party media officer Carrie Johnson, 33, nee Symonds, he has a 16-month-old son, Wilfred Lawrie Nicholas Johnson. The couple revealed in July that another baby is due around Christmas.

The question about the full tally followed a mention of the baby on its way. But the British media in their write-ups suggested he was not counting the one in utero but instead confirming a longtime assumption that he has a daughter from a previous affair.

Johnson said in the interview that he absolutely loved having a baby at 10 Downing Street, but it has involved a lot work. “I change a lot of nappies,” the prime minister said.

The revelation of six offspring was a top story on news sites and broadcasts in Britain.

“I can’t claim to be great source on how many children he has, and I am his biographer,” said Andrew Gimson, with a laugh. He is the author of “Boris: the Making of the Prime Minister.”

Gimson said Johnson’s affairs and marriages haven’t hurt the politician, or not much, “because he’s not a hypocrite. He’s never preached about marriage.”

The biographer told The Post that some Britons may disapprove of having a child out-of-wedlock. Others see his refusal to answer the question as evidence of his slippery nature. “But I think quite a lot of people find it a relief that he is so fallible,” Gimson said.

The prime minister has found himself on the griddle about his personal life. Back in 2004, he denied to the tabloids that he had an affair. Johnson called the story “complete balderdash” and “an inverted pyramid of piffle.” As it turns out, it was true, and he lost a party leadership post over the deception.

In an interview with LBC radio in 2019, during his election campaign, a caller challenged Johnson over a 1995 article he’d written for Spectator magazine, in which he blamed single mothers for “a generation of ill-raised, ignorant, aggressive and illegitimate children.”

Johnson said he shouldn’t be judged by old things he had written — and refused to say how many children he had.

“I love my children very much, but they are not standing at this election. I’m not therefore going to comment on them,” he said.