The bitter rift between pop stars Paul Simon and Art Garfunkel was so vicious that one of their managers had to stand guard to prevent them fighting – and he even believed they were capable of stabbing each other, according to an explosive new book.

In an authorised biography of Simon by Robert Hilburn – serialised in The Mail on Sunday's Event magazine today – the songwriter's business manager Joseph Rascoff reveals: "I genuinely believed that if there had been a knife on the table one of them would have used it."

The backstage clash happened in 1993 when the stars, who had split up in 1970, reunited for a lucrative comeback tour, reports Daily Mail.

Although the pair achieved huge success with hits such as Sound Of Silence and Bridge Over Troubled Water, their feud dated from the 1950s when they performed as an unknown duo called Tom & Jerry.

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Garfunkel resented the extent to which he relied on Simon's songwriting abilities, while Simon was jealous of the attention showered on Garfunkel as the singer. Their success only served to sour relations even more.

The final straw came in 2010 when Simon accused his partner of not giving warning of problems with his voice, which led to the cancellation of a number of shows.

Simon said: "He let us all down. I was tired of all the drama. I didn't feel I could trust him any more."