Dr. Ruth is 91 (which explains the top hat reference), though in matters of sex, she shows no signs of slowing down. Picture: AP

London - As the world’s most famous sex therapist, Dr Ruth Westheimer is the author of more than 40 books, has fronted TV advice shows and met everyone from Princess Diana and Elizabeth Taylor to Presidents Obama, Clinton and Trump.

Yet she remains unequivocal about one of her proudest achievements: "It was wonderful," she says, "to teach the British about orgasms!"

Her TV show, Good Sex!, made for eye-opening viewing when it aired on C4 in the Eighties, but viewers couldn’t help but warm to the diminutive therapist as she talked about "rrrrrelationships" and "errrrroticism" in her distinctive German burr, punctuating her advice with that trademark high-pitched giggle.

She revolutionised the way people talked more openly about sex, "And I loved coming to England," she says. "It made me smile to think of the British with their umbrellas and top hats being in bed."

Dr. Ruth is 91 (which explains the top hat reference), though in matters of sex, she shows no signs of slowing down.

She has just finished work on a new edition of her best-selling book, Sex For Dummies - which even made it into an episode of Friends (Ross was given the guide as a joke, but after impressing Rachel with some new moves, he exclaims: ‘Who’s laughing now?’). 

In June Dr. Ruth was in England to take part in an Oxford Union debate on pornography, "and just last night I was [in a hotel] and plenty of young people recognised me. At the age of 91 and a half - you must say the half - that makes me very happy." 

There is little that doesn’t make Dr. Ruth happy - she is one of the most joyful people you are ever likely to meet. But it is a joy which has been extremely hard won. 

Born in Germany in 1928, the only child of Orthodox Jews, she was just ten when she lost both her parents in the Holocaust. She spent the war in an orphanage in Switzerland then, in her early 20s, joined Haganah - an underground militant organisation fighting for the establishment of a Jewish state in Palestine - and became a sniper, "Luckily, I never had to kill anybody," she says, "but if I’d had to, I could have."

* Ask Dr Ruth will be available for digital download from September 9 and on DVD from September 16.

Daily Mail