Robson Green has said he was once locked in conversation with Cat Stevens for 20 minutes before realising who the star was.
Green was performing with his then band-mate Jerome Flynn on Top Of The Pops in 1995 when he started discussing the music industry with Stevens, also known as Yusuf Islam.
Speaking ahead of the release of the new series of Grantchester, Green, 52, said that Stevens came into their dressing room where they chatted for two hours.
He said: “I only realised 20 minutes into the conversation that it was Cat Stevens/Yusuf. Eventually I asked, ‘What’s your link with the music industry?’ He said, ‘I wrote the song Boyzone are singing’.
“And I suddenly put two and two together and went, ‘Oh my God, it’s Cat Stevens!’”
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Stevens, who has been inducted into the Rock and Roll Hall of Fame, wrote Father And Son and it appeared on his 1970′s album Tea For The Tillerman.
Boyzone reached number two in the UK singles chant with their cover of the track in 1995.