SIX O’CLOCK on a Monday night. A knock on the door. On the step: two detective constables. They show their identification, and ask if they can step inside for a moment to talk to our 13-year-old son, Jamie (not his real name). One of the officers asks: “Are you Jamie Sutton?” He says yes. The officer says: “Jamie Sutton, I am arresting you on suspicion of rape . . .” and reads him his rights.

It was as if someone had driven a tank through the wall. We thought of rape: a violent, aggressive, deviant sexual assault on a vulnerable stranger, on wasteland, in woods, in the back of a van. We looked at our son: a big lad who finds it difficult to conform, but shambling, affable, well-liked, articulate and sensitive. We knew that the charge must be untrue. We were bewildered and scared, and we panicked. We both instinctively foresaw the worst, with cinematic clarity — a miscarriage of justice, imprisonment, and our child irrevocably damaged. Maybe even dead.

My partner and I have always had a hazy, unfocused but generally benign vision of Jamie’s future. Suddenly that collapsed, replaced by a hard-edged image of years of brief contact over a grey utilitarian table in a bleak prison visiting room. In retrospect, it sounds like a pathetic over-reaction. But when the CID enters your home and alleges something so serious, reason deserts you.

Jamie was put in the back of an unmarked car and driven from our small rural town to a police station 14 miles away for questioning. My partner accompanied him. He was put into an adult cell (“He’s a big lad, isn’t he?” they said), then interviewed for 90 minutes. Jamie recalls the fear he felt: here he was in a bleak room with a tape recorder, a solicitor, and two officers playing hard cop/soft cop. He thought of how rapists, murderers and robbers had sat where he sat now. And he hadn’t a clue why he was there.

If he’d been aware of the Sexual Offences Act 2003 (implemented in May 2004) he might have had some inkling. We had never heard of it; you probably haven’t either. The Act changed the definition of rape. “Rape” is now any act of non-consensual penetration — oral, anal or vaginal. Previously, it covered non-consensual anal or vaginal penetration. It might not sound immediately significant to you: it was to Jamie and to us.

Jamie was facing interrogation as a “suspected rapist” because he had met Sarah, 15, whom he knew from school, with a group of her friends in a local park. They did what teenagers do in that fumbling, experimental, exploratory way. She was very drunk, she offered him oral sex, he accepted, the deed was inexpertly done, the two walked back across the park to re-join the rest of the group, and Jamie returned home.

What had happened was a simple excursion into the practical side of sex education that schools don’t teach: something that can be learnt only through experience. You did it, I did it. It is what thousands of teenagers have done, and always will do. It happens every night. Only the most blinkered, ignorant Middle-Englander would consider it an extraordinary occurrence. Two days later, Sarah reported the incident as a sexual assault. The police knew better: this was rape.

As Jamie’s rights were read again and the tape rolled, the detectives probed into the most intimate sexual details relating to the incident and Jamie’s past experience. His mother and the solicitor intervened as the police laid on emotional pressure. They asked him to speculate on whether she was a virgin, to speculate on how her parents would have felt when faced with the situation. Finally, they asked — gratuitously: “If you had a sister, and she related this to you, how would you feel and what would you do?” Yes, well, what would you do?

Jamie mildly told them that he would make absolutely sure that the accusation was founded in fact before doing anything at all. Then he would stop and think. It was mature advice in response to a wholly unreasonable question. Maybe these officers should have taken note.

Throughout the interview, our son answered the officers quietly, articulately, and with self-control. Looking back and listening to the tape, we are proud of him, but to have our pride in our son’s strength and resolve confirmed in such appalling circumstances is bitterly painful.

Jamie and his mother returned home, emotionally and physically shattered. Together, while images of prison cells still haunted us, we fought to pull this back to the essentials: one park, two teenagers, some sexual experimentation, full stop.

Jamie insisted on attending school: he had nothing to hide. The girl also attended school, seemingly unaffected by events. Tribal alignments were forged in the corridors. We coped by doing whatever we thought might help: meeting the school, meeting a solicitor, trying to find out what might happen as the case progressed. But there was only so much that we could do, and then a weird and contradictory mix of anger and listlessness took over.

Everyday tasks went by the board: the takeaway containers piled up in the bin, clothes went unwashed, the house was a mess. Our physical existence was thrown into a disorder that reflected our mental state. We had no idea how long this might last.