Prince Charles was 'all over Diana like a bad rash' when the royal couple first courted but after a sizzling start their marriage turmoil saw their sex life fizzle out.

The Prince of Wales could not keep his hands off his future wife after kissing her at a polo match, with Diana describing the thrill of speaking to Charles as 'immense and intense'.

The Prince and Princess of Wales' marital woe and sex life is laid bare in a new Channel 4 programme, drawing on taped sessions between Diana and her voice coach.

Early days: Prince Charles was 'all over Diana like a bad rash' when the royal couple first courted (Left, Charles and Diana share a kiss at a polo match in 1984 and right, before their wedding in 1981)

Diana, who died in a 1997 car crash in Paris, candidly discusses the breakdown of intimacy with her husband, claiming that they went from having sex 'once every three weeks' to it fizzling out all together in the late 1980s.

The Princess hired Peter Settelen between 1992 and 1993 to help with her public speaking voice, but their sessions became a place for Diana to reveal her inner anxieties and personal unrest.

Key revelations from the documentary on their sessions, Diana: In Her Own Words, include:

When Diana confronted Charles over his affair with Camilla he said: 'I refuse to be the Prince of Wales who never had a mistress.'

Princess asked the Queen for marital advice only to be told 'Charles is hopeless'

Diana battled bulimia triggered by marriage and isolation from Royal family

Princess fantasised about running away with bodyguard Barry Mannakee

Diana also discusses how she met Charles and reveals that the pair only spent time together on 13 occasions before they got married.

She said: 'I was asked to stay with friends in Sussex and they said, ''Oh, the Prince of Wales is staying because he's playing polo.''

'I thought I hadn't seen him in ages. He had just broken up with his girlfriend and Earl Mountbatten had just been killed.'

Whirlwind romance: Diana said that her and Charles (pictured, on their wedding day in 1981) met only 13 times before they got married

She revealed that she hadn't been that taken with the Prince on previous occasions, but this time her feelings changed.

Diana said: 'I am quite impressed. He chatted me up, [he was all over me] like a bad rash; I thought...ehh [pulls back, pulls face].

'We were at a barbecue that night talking about Mountbatten and his girlfriend and I said, ''You must be so lonely.''

Troubled: Princess Diana talks to her husband Prince Charles at a Polo match in 1985

'I said, ''It's pathetic watching you walking up the aisle with Lord Mountbatten's coffin in front, ghastly. You need someone beside you...''

'Agggh. Wrong word! Whereupon he leapt upon me and started kissing me and everything and [waves arms] urrgh...You know, this is not what people do.

'Next day he said, ''You must come to Buckingham Palace with me, I have some work to do but you wouldn't mind sitting while I do my work.''

'I thought, ''Well, bugger it, I do mind sitting there while you do your work,' and I said that and it sort of lit up something in him, that someone answered back. So I was quite a challenge.'

She added: 'He wasn't consistent with his courting abilities.

'He'd ring me every day for a week, then wouldn't speak to me for three weeks. Very odd. I thought, ''Fine. Well, he knows where I am if he wants me.''

'The thrill when he used to ring up was so immense and intense. It would drive the other three girls in my flat crazy.'

When her voice coach suggested there was virtually no sexual relations between her and Charles, Diana replied: 'Once every three weeks and then it fizzled out about seven years ago, six years ago.'

Exciting: Diana said when her and Charles first courted the thrill of their conversations was both 'immense and intense'

Diana later speaks candidly about her battles with an eating disorder telling her speech coach: 'Everybody knew about the bulimia in the family and they all blamed the failure of the marriage on the bulimia, and that's taken some time to get them to think differently.

'I said I was rejected, I didn't think I was good enough for this family, so I took it out on myself.

'I said 'I could've gone to alcohol, which would've been obvious, I could've been anorexic, which would be even more obvious.

'I decided to do the more discreet thing, which ultimately wasn't discreet but I chose to hurt myself instead of hurting all of you'.'