It’s the split-second incident that someone recalls, sometimes long afterwards, that often unlocks a mystery. A signalman at Camden Town, London, remembered that as a train shuttled past his box at 2.14 p.m. on Friday, January 9th, 1914, he saw a man leaning over a child in a third class compartment near the engine. The train was later searched, and under a seat police found the body of five-year old Willie Starchfield. He had been strangled.

Chief suspect was John Starchfield, the boy’s father, who sold newspapers in Tottenham Court Road. Starchfield was estranged from his wife Agnes. He was charged with Willie’s murder at the Old Bailey, but the judge soon stopped the trial for lack of evidence.

On the afternoon he died Willie had been left in the care of his mother’s landlady while his mother went out job hunting. There was some evidence, in fact, that an unidentified woman who had been seen locally may have killed Willie. A witness said: “I saw her take him by the hand and then she was tugging at him. I don’t think he wanted to go with her.”

Ironically, Willie hadn’t got long to live anyway. Pathologist Sir Bernard Spilsbury said: “He was suffering from a heart condition by which any sudden or violent shock was likely to kill him.”

How he came to be on the Camden Town train, why he was murdered and who was responsible remain mysteries to this day.