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The news was announced on Wednesday on the Norwegian synth-pop band's official website in an article written by their biographer Jan Omdahl, which also revealed the singer had already undergone brain surgery twice.

"This was downtime for them in a very busy time and it was an attempt to be discreet," said Mark Lewisohn, a historian, biographer and well-respected authority on the Beatles.

"We need a new generation of political leaders who are up to the challenge," says political historian and biographer Sir Anthony Seldon.

And yet, as the band's only official biographer Hunter Davies told Radio 4's Today programme on Wednesday: "The strange thing about the Beatles is that the longer we get from them, the bigger they become".

"Philip had a rather tragic and lonely childhood," said historian and Philip's biographer Prof Angela John, who acted as an informal consultant on the film.