Robert and Patricia Seddon

Sale, Greater Manchester, July 2012.

Robert and Patricia Seddon, sixty-eight and sixty-five, married for forty-seven years, are found shot dead in their home on Clough Avenue. A shotgun lies across Robert's lap, and the scene tells a simple, dreadful story of murder and suicide.

It is a lie. Four months earlier, a hired BMW carrying the couple and their grandson had plunged into the Bridgewater Canal, and the man who climbed clear, then posed as a hero on the sinking roof, was the same man who stood to inherit everything: their son.

This is the story of Stephen Seddon, of the parents who gave him money, houses and unconditional loyalty, of the father who worked out the truth and confided it to his doctor the day before he was murdered, and of the trial that ended with a life sentence and a minimum term of forty years.

When someone kills their parents, you imagine a “reason” – escaping abuse, for example. I struggle to understand why a son raised by a couple who were by all acounts loving and caring would plot their deaths purely for money. If Stephen had asked his parents for help, it seems like he would have received it.

The thing I keep coming back to is Bob, who had worked out what his son was up to, and confided in his GP. What a heartbreaking position to be in, and what a shame that it wasn’t enough to save him and Pat.

Most of this episode is drawn from the sentencing remarks, which are unusually full. The video interview Stephen Seddon gave on the towpath after the canal incident can still be watched, and knowing what came later, it is one of the hardest things in this case to look at.