Princess Diana's former butler has claimed that Pakistani heart surgeon Hasnat Khan was the princess' only true love after her divorce from Prince Charles and that she was desperate to marry him.

In an interview with ABC's 20-20, scheduled to be broadcast on American television October 25, Paul Burrell reveals that Khan was one of nine suitors -- the others were an Oscar-winning Hollywood actor, a famous politician, a lawyer, a top musician, a sportsman and a novelist.

But he confirms that of all of them, Khan was 'the favourite'.

Burrell tells show host Barbara Walters, 'She was a busy lady; all these different men interested her. I'm not saying she had affairs with these men. They were suitors.'

In the latest extracts from his book A Royal Duty published in the Daily Mirror, Burrell also says the princess was never in love with Dodi Al Fayed, with whom she died in a Paris car crash in August 1997.

'Just as she had compartmentalised certain friendships, she controlled the position of her gentleman friends,' Burrell writes. 'We called it 'the trap system', as if the men were competitors on a racetrack, running round after the princess with their gifts and flowers.

'The occupant of Trap No 1 never changed. He remained in pole position in the princess's eyes, not threatened by those on the periphery. Throughout the day I kept the princess informed about which trap had rung and at what time. "Trap No5 has rung, he wants you to ring him back. Trap No 8 wants to speak to you, shall I put him off again?"

'On her writing desk the princess kept a list of the traps and their occupants. In my pantry a duplicate of the same list, which changed as men fell in and out of favour, was tucked into the back of my desk diary.

'Sometimes the princess could not believe how many suitors were making their intentions known. She used to joke that the racecourse was getting "a little overcrowded".'

On ABC's 20-20 programme Burrell defends his decision to write about Diana's personal affairs, hopes and fears, including the letter in which she predicted her death in a car 'accident'.

He says, 'I struggled so long and so hard with this, wondering what to do with it. If I gave it to the wrong person it could be shredded, it could be erased, it could disappear.

'I think it's an important letter. It's there in the public domain and now we will have a proper investigation.'