The story about the human sexuality class at Northwestern University, Chicago, is just the latest to underline how frightened and guilty so many people are when it comes to sex. For those who missed it, it appears that on the 21st February Professor John Michael Bailey allowed a couple to demonstrate the use of a vibrator in front of about 100 students. The couple, named as Jim Marcus and his fiancée Faith Kroll, volunteered, and the students had been warned to leave if they objected. So it’s difficult to see why so many parents and commentators complained so strongly. The professor himself said he would give an F grade to the arguments put forward by his critics. Quite right.

The first school lesson I received in sex involved frogs. I spent the next few months under the impression that human sex was accomplished on Sunday nights, with the man clinging to his partner’s back while she crawled around the bath.

Several columnists recently have anguished over what to say to children who accidentally come across sex scenes on the internet. Well, why not explain that the people are…having sex? Is that so terrible?  ‘They’re having sex, which is a lovely and beautiful thing that you’ll be able to do when you’re older.’

The secrecy and embarrassment causes children to think that there must be something wrong with sex. They grow up feeling guilty and inhibited and, in turn, pass on their anxieties to their children. The cycle is endless and it causes a lot of misery.

Incidentally, Faith said that she was an exhibitionist and was turned on by having an audience watch her naked with the vibrator. Try using this as a fantasy next time you have sex and see what happens.

Sex was pretty soon the topic of conversation when we had a few friends around for dinner last night. I’ve got quite skilful at cajoling people into revealing what they do and what they don’t do. Occasionally someone will say, ‘People who talk about it don’t do it.’ But, of course, that’s not true. Do you know people who talk about skiing if they don’t go skiing?

‘I don’t understand the point of Tantric sex,’ said J, who knew I’d written a book on the subject. ‘It would be like coming for dinner and not eating anything.’ He gestured at the food my partner had prepared.

It’s a common misconception that Tantra is all about non-ejaculatory sex, but I let that pass. J is over 80 so I pointed out to him that by not ejaculating he’d be able to have sex for longer and more frequently. At this G, who is pretty young, interposed that he neither wished to have longer sex nor more frequent sex, and his even younger partner nodded in agreement.

I’m always astonished how infrequently most couples have sex and how little time they spend over it.

‘You could have sex every day,’ I said. ‘Wouldn’t that be great?’

‘That would just be boring,’ said H.

H had already told me that he’s had sex with over 300 women so his opinion counts for something. But he’s wrong on this.’You eat three times a day and don’t say that’s boring,’ I pointed out. ‘If you don’t ejaculate you can turn a snack into a banquet that goes on for an hour, two hours, three hours…’

‘Ah! Terrible!’ said E, who is G’s partner. ‘I’d just get sore.’

‘Could someone just pass me the olive oil?’ I asked, and trickled some onto my pasta. ‘That,’ I said, ‘is the secret. Plenty of lubrication.’