Sport on TV: Daley deeply embarrassed, yet it's much darker for black belt

There aren't many similarities between Tom Daley and Tiger Woods, apart from their sheer talent, and long may it stay that way. True, the 15-year-old pubescent prodigy may find his mind drifting off from his training to think dirty thoughts – he does spend all day with hardly any clothes on, after all – but he must sincerely hope that his father doesn't come back to haunt him from beyond the grave.

On Olympic Dreams (BBC1, Tuesday), Daley has a teenage cringeing embarrassment at his dad's antics down to a tee, culminating in the moment when Rob showed up at the press conference after Tom won a World Championship gold medal last year and insisted on having a cuddle. "Not cool, at all. Not cool."

Rob pulled him out of school after his classmates starting calling him things like "diver boy" and "Speedo boy", as well as "throwing paper and emptying pencil cases". And then there's his thunderous but utterly tuneless renditions of the national anthem.

He has seen every dive Tom has done since his first training session, but four years ago he was diagnosed with a massive brain tumour and he thought he would never get to see his son perform at the Olympics.

Fortunately, Tom got there early, aged 14, since when his father has recovered. To think it was Daley's synchronised diving partner Blake Aldridge who mucked it all up in Beijing by ringing his own mother in the middle of the competition. Daley must have hoped that a big hole would open up for him to dive into.

He is now cocooned in a private school and says things like "It doesn't feel like it's happening to me, it's happening to another Tom". But the Olympic dream is rather more of a nightmare for little-known aspiring judoist Ashley McKenzie. When we meet him, he is serving a ban for "drinking, breaking curfews, being rude and smoking". Dream on, Tom.

Ashley was diagnosed with Attention Deficit Hyperactive Disorder and his medication is banned by the International Olympic Committee, but the British amateur governing body give him special dispensation to keep taking it for the national trials. He decides not to take the risk and gives up the pills.

Then in the final of the trials, "he got kicked in the nuts and booed by an entire crowd", according to his mum. "What do you want from him?" He loses, flicks the finger at the judges and is disqualified.

The British Judo Association keep reaching out to him, and include him in their World Cup squad as the most improved junior at their academy. But the day before the match, his single mum has to throw his brother out of the house.

McKenzie loses in the first round but manages to keep his temper. He still has a fighting chance but he has a horde of demons to grapple with as his male role models disappear into the distance.