Just as this horrific story of the murder of Rachel Nickell and the subsequent half-botched investigation had almost reached its conclusion, the last ad break featured that Barnardos advert. Blimey. Just as I thought I couldn’t take it any more, just as I thought humanity couldn’t get any more buggered, there were graphic shots of someone battering his partner. This, coupled with this True Crime programme, left me needing a sit down in a darkened room for a while.

True Crime programmes are weird. Why do we watch them? Because they give us glimpses to a dark side of the human personality that most sane people would never dare to go to? Do they make is feel safe, knowing that all the badness is out there and not in our living rooms? Is it to do with a warped sense of voyeurism? Is it purely that people like to watch things about police and find out the way they caught the bad guys? Or is it some sort of emotional displacement thing?

I don’t know, but with programme about gang rape on Channel 4, Panaorama investigating suicide bombers, Monday night on telly was hardly laugh-a-minute.

But that’s ok. TV is for serious stuff too, and you couldn’t get more serious than this – a run-down of what happened to Rachel Nickell, a young and beautiful mum, in 1992 at a park in Wimbledon. She was murdered brutally in front of her two-year-old son, and the man who did it wasn’t caught and convicted until last year.

Rachel’s partner, André, explained to Mark Austin the immediate aftermath and how he contemplated killing himself and his young son, because he felt there was nothing left for them. It just made you think.. how on Earth would someone cope with a sudden and terrible loss like that, knowing that the love of your life had not just been murdered, but murdered so sadistically in front of your son? It beggared belief.

So that was the first bit of the programme – going for the emotional sucker punch (and succeeding) and setting the scene, reminding us what a lovely woman Rachel was. André, you realised, was a man of huge courage and dignity.

But what he hadn’t bargained for was the police investigation that followed. After coaxing a description from his young son, the police got to work and zeroed in on a man called Colin Stagg, who they were convinced carried out the murder. A police psychologist, who was roundly criticised throughout this programme, had suggested using an undercover female office to to and provoke some sort of confession from Stagg. It didn’t come and eventually Stagg sued for 700 grand.

What that particular branch of police had failed to realise, was Rachel’s killer had actually been the same man who was raping and murdering people in the next district. How these two cases weren’t connected was beyond anyone, and a young mother and her daughter would have been saved if all efforts weren’t focused on nailing an innocent man.

Still, it did make for interesting viewing. There’s no point doing things like this if you’re just going to rehash old, tabloid stuff, but I really did learn things - stuff about Rachel, stuff about André and stuff about the case itself. So it did the job in a televisual way, but at the heart of it all was just an appalling and inexplicable loss of life, which André amd his son had, somehow, managed to survive.