Another sign of big boy’s burgeoning sexuality is the fact that he now seems to be perpetually embarrassed: embarrassed about bodies, embarrassed about girls, embarrassed by any discussion of sex. The other night, for example, I invited him to watch the BBC programme about teenage boys with me.

All was well for the first ten minutes or so but then suddenly, there was a naked teenage torso, complete with teenage genitalia and a clever graphic demonstration of the development of said genitalia. Big boy hurriedly covered his face with a cushion and began to roar.

“Urgh!!! That’s disgusting! That’s totally bloody disgusting. How can you watch that! It’s perverted!”

As the demonstration continued with the development of the testes, big boy fled the room in horror and returned to the safety of his own room and MTV.

It’s some time now since I saw him without his clothes on – years in fact. Yet it seems only yesterday that I battled with him to keep his trunks on on beach holidays or ordered him not to run round the house starkers when certain visitors came. I have never forgotten him at my sister’s wedding party one very hot day in my parents’ garden. There we all were in our floaty finery, tucking into poached salmon and quaffing champagne. Suddenly big boy and bro appeared on their little bikes with nothing on. They cycled around the party going from table to table, offering the guests apples from the wicker baskets attached to the front of their bikes. Most people didn’t seem to mind but a few of the elderly relatives looked like they might choke. It was a battle to get them clothed again.

Big boy’s reaction to the teenage willy on TV was not something unknown to me. He now responds in a similar way if he catches me without my clothes on or even in my underwear. I try not to offend him and make great efforts to stay fully clothed around the house but accidents will happen. The other morning for example, hurrying to get ready for work, I ran downstairs to fetch some clean clothes from the drier, wearing a t-shirt over my bra and pants. I then stupidly attempted to dress in the kitchen where big boy was slurping down a glass of milk. The reaction was predictable:

“Yuk, Mum, go away. Can’t you see I’m havin’ breakfast? Errr, I’m goin’ to be sick.” He duly made loud retching noises and turned his chair around to face the wall thus avoiding the shocking sight of his mother’s bare legs.

These days he barricades himself in the bathroom and shouts warnings to anyone going past the door to stay away, even though the door is locked. If he forgets to take a towel in with him, he will yell at us to clear the area as he exits the bath, dashing swiftly up the stairs to his room with his hands firmly clasped over his very own teenage willy.

As for girls, I’ve noticed that he gets very embarrassed in certain situations, for example, if he sees a pretty one, or a large group of girls together. What makes it worse for him is that he knows I’ve noticed so that going out for a meal or going shopping together can become an excruciating experience for him. The other night we went to our favourite pizza place and as we were tucking in, a group of teenage girls were placed at the table next to us. For bro this was a great excuse to start showing off by pulling faces and making himself burp very loudly but for big boy it was torture. He squirmed about in his chair, he seemed to lose his appetite and he didn’t know where to look. At the end of the meal, he rushed out of the place with his cheeks burning and his eyes firmly fixed to the floor. He didn’t even wait to get his free lollipop!

All of these developments have made me wonder if sexual experimentation is about to move from the realms of fantasy to messy adolescent reality. People have always said to me that it’s much more of a worry if you have a teenage girl but I’m not sure about that. It must be awful if your teenage girl suddenly announces that she’s pregnant. But it’s surely just as awful if a teenage girl suddenly announces that she’s pregnant by your teenage son. And of course, either way, boy or girl, they can both catch things….

With this in mind and with big boy about to head off for two weeks in the sun with his Dad and bro, I decided that we needed to have a chat. About condoms.

“Do you know how to use a condom?” I asked him the other night when we were alone.

Suddenly, a look of complete horror came over his face.

“How can you? That’s sick, that’s bloody perverted! You’re paedophile. How can you say such a fing? I’m only a child!”

“Because you’re nearly fourteen, because you look fifteen and because in a few days you’ll be lying on a Mediterranean beach surrounded by semi-naked girls. You never know what might happen.”

“Aaaagh, I’m not talkin’ to you,” he said and ran out of the room.

Clearly, this was a big mistake and I began to feel like Eddie out of ‘Ab Fab’ who was always trying to encourage the virginal Saffie to get on and lose it. To be honest, I felt terrible that I had been so insensitive. Even so, a packet of condoms will be finding its way into his luggage. Just in case.

Rebecca Misell lives in London with her two sons aged 11 & 13.

NEXT INSTALMENT: THURSDAY 8 AUGUST