Last Night's TV: Britain's Lost World BBC1The Flapping Track BBC4

I used to feel rather cross with Bill Oddie for being mean to Kate Humble on Springwatch, but five minute into Britain's Lost World I was coming round to his point of view. Humble was off to visit the islands of St Kilda, stuck out in the north Atlantic, west of the Hebrides. It is, Humble announced, "the most secret place in Britain"; when the inhabitants evacuated the place in 1930, they "left behind a place full of secrets"; and now, along with Dan Snow and Steve Backshall, she was going "to explore, to experience and to unravel the secrets of St. Kilda". Look, the place is marked on Ordnance Survey maps, it's been the subject of a well-known film by Michael Powell and documentaries on Radios 3 and 4, and it has its own, quite long and detailed Wikipedia entry. It's not as if they were going to spend 10 days wandering around the laboratories at Porton Down. St Kilda is only a secret if you define secret as "not previously the subject of a three-part prime-time terrestrial television series", which is not what it says in my dictionary. Meanwhile, the interminable background music kept switching between faux-Celtic melancholy and by-numbers elemental majesty.

All of which was rather a pity, because when it wasn't trying to convince you that it was a summer action blockbuster, this was an interesting programme. St Kilda is a naturally telegenic spot, a cluster of rocky outcrops left behind by a giant volcano, with sea-cliffs three times as high as the white cliffs of Dover, their tops almost perpetually lost in a haze of cloud, the air thick with seabirds. The seabirds are, by the way, the solution to most of St Kilda's supposed secrets. They're what the inhabitants lived on, abseiling down those cliffs to slaughter and collect them by the hundred, and then use them for meat, for fuel ("Chuck another puffin on the fire"), for fertiliser to grow the islands' meagre crop of barley. This last may be the key to the islanders' desertion. From the mid 19th century, the barley crops shrank, and a swift analysis of the soil in the islands' single field showed that it had toxic levels of lead and zinc, which must have come from all those corpses.

But in any case, it is a horribly isolated spot. At one point, Backshall travelled from the main island, Hirta, out to Boreray, a towering rock four miles across the ocean, to spend a night alone with the seabirds. The trip out provided the programme's highlight, as Snow tried to row him there in a boat that he apparently hadn't bothered to check for leaks. As he rowed and Backshall bailed more and more frantically, the compulsory bantering tone became increasingly strained, until they were forced to abandon ship and be picked up by a boat that had presumably been waiting there just in case. Once on Boreray, Backshall discovered that approaching storms meant no boat would be available to carry him home, and if he wasn't rescued soon he faced the prospect of being stuck alone, without supplies, for several days. Instead, a Coastguard helicopter winched him off. Earlier, Backshall had tried to talk up the elemental pleasures of the islanders' lives compared to the "banality" of life on the mainland, but he also told the story of a group of the islanders who travelled to Boreray in the early 18th century, and were marooned for a full nine months, living on raw gannet flesh, as smallpox devastated their home village. Presumably, they would have taken banality and helicopters any time. And here is another part of the solution to the supposed mystery of why the St Kildans left. I had thought that there wouldn't be enough material to keep the programme going a full hour, but now I'm wishing they'd cut out the hi-jinks and just got on with the wildlife and the history, because they won't be able to fit it all into the two programmes they've got left.

Another piece of vanished, or at any rate, vanishing heritage was uncovered in The Flapping Track, a documentary by Daniel Gordon that was the centrepiece of an evening devoted to dogs. "Flapping" is the name given to unregulated (but legal) greyhound racing. Sixty years ago there were more than 130 of these tracks, nearly all in Scotland or northern England. In 1984, when the miners' strike started, there were less than 60; now it's down to 11. The film was set at Highgate stadium, midway between Barnsley and Rotherham, run by George Russell, nicknamed "Tricky Russ" because he is regarded as, to quote one regular, a "scamming bastard". Much of the film's appeal lay in the frank way everybody – dog owners, punters, bookies – discussed the various methods of cheating, particularly in the handicap races, and nobody cared: shove a bit of lead in your dog's muzzle in the heats, or introduce a slow ringer, or feed your dog up just before the main race, then bet on the competition, it's all part of the game. It lost its touch somewhat when it started to harp on the uncertain future. And while Nick Bennett filmed it beautifully, crisp colours under floodlights, it was spoiled by some Guy Ritchie mannerisms – freeze frames, an over-loud rock soundtrack. One Guy Ritchie is more than enough.