When Sebastian Coe agreed to take part in Who Do You Think You Are? (BBC1, Wednesday), he may have thought it would make a pleasant distraction from organising London 2012, but there was no running away from his past. He is forever being asked about the legacy of the Olympic Games, so it was no surprise that he should find himself poring over the last wills and testaments of his forefathers to find out what they left behind. It was to be a legacy of leg-overs and leg-chains.
If ever character traits were to run in the family, you would think it would happen to the former gold medallist. They all have protuberant noses. But he takes more pleasure from discovering that his mother's ancestors lived in Jamaica, "the powerhouse of world athletics". They were sugar plantation owners with more wealth than the aristocracy because sugar, known as "white gold", was in huge demand back home. One of the plantocracy's brood, Hyde John Clarke, was born in Trelawny, the parish that produced Usain Bolt.
The Hyde Clarkes also poured their money back into the British economy to fuel the Industrial Revolution and set up a stately home at Hyde Hall in Cheshire. "I think I raced there as a kid," says Coe. "It was 30 miles from where I did all my training."
Hyde John Clarke left the sugar behind to become a Navy captain and then a benefactor back in Blighty. It's surprising he didn't run for office. Coe said: "I've always naturally been drawn to people who have contributed." Not least those who handed over their bank details to buy tickets for the Olympics.
But there is a darker side to this story: the sea captain was one of six illegitimate children fathered by George Hyde Clarke, the plantation owner who enjoyed all the fruits of a decadent colonial existence, and who was variously described in the wills as an "execrable villain" and a "profligate, abandoned nephew".
Over everything hung the spectre of slavery. George had hundreds of slaves but it was his father, Major Edward, who felt their resentment most keenly. He was the lieutenant governor of New York in 1741 when a slave uprising in the fetid swamp that was Manhattan led to vast swathes of the nascent city being burned to the ground.
The Major's solution to the problem of finding the ringleaders of the riot was to offer slaves their freedom and a £100 lump sum, three times the annual wage of a skilled artisan. The culprits were duly identified and executed, and New York was saved as a colonial outpost.
So if anyone is thinking of burning down a few of the constructions taking shape in the fetid swamp of London's East End, they had better beat a hasty retreat because Lord Coe will be hot on their heels.
Gavin Henson is a sportsman who might qualify for "who do you think you are?" in the other sense. Right now he would be hard-pressed to trace his own rugby career, let alone his family tree. As the Wales players head off to the World Cup, he's strutting his stuff on The Bachelor (Five, Friday), perhaps planning to expand his own dynasty quite soon.
He ditched 10 of his 25 suitors straightaway, including identical twins, though it was unclear if they came as a package. But this series will still drag on longer than the Dragonhood's World Cup campaign.