It seems people have been losing their virginity at an ever lower age since the Thirties. So while women who are now 60 usually lost their virginity around 21, these days a quarter of all men born in the early Seventies - older than Dilly's son - had lost their virginity before 15.
So though what's happening in Dilly's family isn't yet usual, it's by no means unusual. And readers, who can view the situation objectively, were by and large liberal and comforting.
But it's one thing to be an objective reader. You'll find the hair of most parents, faced with a similar problem, coming out in handfuls. Have they given birth to a cad, a bounder, a sexaholic? If she's anything like me, Dilly's probably letting her mind run riot, frantically working out how she could look after twin grandchildren while nursing a son with Aids and getting him through his GCSEs, all at the same time.
Calm down, said Julia May of Bath. 'Don't say anything to anyone until you have got over the shock. Remember that as crimes and misdemeanors go, what your son is doing isn't as horrifying as stealing cars, bullying or taking drugs, and some 16-year-olds, who can legally have sex, may well be less mature than your son.'
Everyone agreed that to tell the girl's parents - something Dilly had on her mind - was the last thing she should do. After all, it might only be a rumour, put about by vicious friends; or her son might be more boaster than bonker.
Where readers' views diverged was on whether to talk to the son directly. John Thorne of Dunkeld, Perthshire, advised: 'Give him a gross of condoms and offer to buy a double bed for his room . . . This isn't so much encouragement (if you tell him not to, he will simply do it anyway) as a starting point for open discussion.'
A gentler suggestion came from an anonymous reader from Marnhull, Dorset. 'The parents must bring the subject up and remind their son that though they know him to be both physically and intellectually mature, he might find the emotional side of this commitment a bit tricky at times; and if he wants to talk to them about it, that's fine.'
Susie, 14, sounded fantastically mature. 'First, I can imagine that any parents who think their son is having sex would be worried and come down on him straight away,' she wrote. 'Talk to him, but don't get too personal or graphic; this might embarrass him. Don't go to the girl's parents without talking to him first. I think that would seem sneaky and break down any trust. But if he admits it, make sure he uses a condom, the best protection against Aids and pregnancy.'
That this event was an emotional milestone not just for the boy but also for his parents was pointed out by Pat Hurford of St Albans. 'Dilly and her husband are being pushed into another stage of emotional maturity - as we all are by our children - and that is often painful.'
Some felt that what was going on signified the beginning of the end of the days when Dilly and her husband could dictate their son's behaviour. Breaking the sex barrier is a real sign of separation, a moment when the task of 'hands-off' parenting has to begin.
And it works both ways. 'Direct questions about sexual habits cause offence. Imagine how you and your husband would feel if your son were to quiz you about your sexual past or current practices,' wrote Julia May. And Alison Hadley of the Brook Advisory Centres, where young people are counselled in sexual matters, was against talking to the boy directly. It was, she felt, the girl's age - 13 - which was the real frightener for his parents. 'But it really depends on the maturity of the girl. The boy may be mature, but he wouldn't be alone in feeling unable to discuss this kind of thing with his parents. That's why they should bring the subject up in an indirect way - perhaps prompted by something they see on television or in a magazine.
'Saying they know because someone's told them would only make him angry or more secretive. But they should get the information over to him that girls under 16 can go to doctors and get contraception in confidence, and they should discuss condoms as a method of birth control.
'As for the legality of it, although it's illegal for a man to have intercourse with a girl under 16, the law becomes very grey if the boy himself is under 16. It would be unlikely to lead to a prosecution.'
Having sex is a bit like learning to ride a bicycle. You can't unlearn it. If these two children find sex is enjoyable and loving, they'll find a way to have it even if their parents impose curfews and string barbed wire on their bedroom windows. But if his parents start talking suddenly about underage sex and contraception generally, their son will realise that they know what he's up to. Depending on their views, he'll probably find out whether they think it's a good idea or not, and also know, by the fact they don't refer to it directly, that they realise that they can't put the clock back. But at least he will know one thing: that they love him enough to be concerned that he and his girlfriend are safe.
MY next-door neighbours are reasonably pleasant, fit and in their fifties. In their front garden they have parking space for their two cars - but nine times out of 10 they only use one car. Instead of parking their second car in their garden or in front of their own gate, they park it in front of our house, which has no front garden. This drives me insane. Parking is incredibly tight round here, I have a small child and often heavy shopping, and I frequently have to stagger down the road with everything, having been forced to park much farther up.
Yes, the solution is to ask them nicely whether they would park in their garden or in front of their own gate. Or I should park in front of their gate, ring their bell and explain that I'll move if they want to get their car out. But I am reluctant to do this - it seems so confrontational. Do other people feel as strongly about parking in their street?
Please send your comments and suggestions to me at Features, the Independent, 40 City Road, London ECIY 2DB (fax 071-956 1739), to arrive by Tuesday morning. And if you have any dilemmas that you would like to share with readers, let me know and I will report back next Thursday.