Sport on TV: A man caught between the devil and the deep blue sea

Peter Nichols' book about the Golden Globe round-the-world yacht race of 1968-69 was called "A Voyage for Madmen", and he wasn't wrong. Of the nine adventurers, one finished – the redoubtable Robin Knox-Johnston. One hanged himself. Another, Bernard Moitessier, the Frenchman with the soul of a poet, turned round within sight of victory and did it all again. Five abandoned, beaten by the cruel seas.

And then there was Donald Crowhurst. The failed businessman and weekend sailor saw the race as his one shot at glory. Instead he broke the rules, went bonkers and slipped over the side of his rickety trimaran.

Preparations were farcical. "He'd lost track of what was happening on his boat," the BBC man Donald Kerr told the makers of Deep Water (Channel 4, Monday), a riveting account of Crowhurst's story. "I told the cameraman, 'this isn't going to succeed. Film the chaos of it all.'" And Crowhurst's wife Clare recalled: "People were saying to him, 'Is everything all right? Are you sure what you're doing?'"

On the eve of departure, 31 October, the very last possible day under race rules, he walked with Clare and Kerr on Teignmouth beach. He was trembling, saying, "I can't go. The boat isn't ready." They met Stanley Best, his backer, and Rodney Hallworth, the Dickensian character who was doing his publicity. They bullied him into going. That night, in the bedroom with Clare, he wept.

Within five days he was recording in his log: "This bloody boat is falling apart." His contract with Best stipulated that if he turned back he had to buy the boat off him, which would bankrupt him. And if he went on to face the Southern Ocean he was toast.

But he had a cunning plan. He began to send back false reports – 172 miles one day, a world record 243 the next. And then he went into radio silence for the winter, pootling around the coast of South America and waiting for the others to come round Cape Horn. Then he'd slip back into the field.

However... Moitessier had gone AWOL, so ahead of Crowhurst Knox-Johnston was going to be first home while Nigel Tetley, who'd left after the future knight, was on to take the £5,000 prize for fastest time. Then Tetley sank. Now Crowhurst was in the frame: his logbooks would be scrutinised; he would be exposed.

His boat was found drifting. His log, filled with insane ramblings, seems to record a descent into madness. I'm not so sure: much of it sounds like someone trying hard to sound a few hulls short of a trimaran. Was he copping an insanity plea?

One thing is for sure: "Anyone who does this race for money or fame will come to grief," Moitessier said beforehand, and he was right about Crowhurst.

Knox-Johnston, the sanest man in the whole story, won the £5,000. He gave it to the dead man's family.