Granville Jenkins, a 45-year-old wages clerk, was helping a farmer friend at St. Brides, near Newport, Monmouthshire. It was JUNE 12th, 1954, and the farmer asked him to lead a horse from the farmyard to an outbuilding a mile away where the farmer would pick him up in his lorry.

But as the farmer drove to collect him, he saw the horse approaching him unattended. He stopped his lorry, caught the horse, and looked for Jenkins. A haversack and a letter from the Newport unemployment office lay at the roadside, and a trail of trampled grass led him to a stream where he found Jenkins’s dead body. The wages clerk had been stabbed 32 times and his throat had been cut, but the motive was a mystery, because he had not been robbed.

Police searching the area cornered a man whom they recognised as Tahir Gass, an unemployed Somali sailor who had caused a disturbance in Newport two days earlier. As they approached him he produced a knife, but he dropped it when they drew their truncheons.

Gass’s overcoat had been found at the crime scene, and he was arrested and charged with Jenkins’s murder. At his trial the court heard that while in custody he had claimed that the police were giving him electric shocks. For that reason he could not be left in a room with electric fittings, for he destroyed them.

Placed in a padded cell, he had wrecked it trying to get out, saying that four men were going to rape him. He claimed to be the son of the king of Somalia, and to have killed 2,000 white men and 1,000 black men while fighting for the British in the Second World War.

A medical witness testified that Gass was schizophrenic, always carrying a knife because of his obsession that he would be raped. That was enough for the jury. They found Gass guilty but insane and he was committed to Broadmoor.

A year later he was deported to his native country, but the authorities had not heard the last of him. In 1998 his name resurfaced when the Court of Appeal considered the case of another Somali sailor, Mahmoud Hussein Mattan, who had been executed in 1952 for the murder of a Cardiff shopkeeper. It had since emerged that Gass had been observed at the crime scene, and Mattan’s conviction was quashed as unsafe – 46 years too late to save him from the gallows.