Last Night's TV: Living with Brucie, Channel 4<br />John Sergeant on Tracks of Empire, BBC4

Living with Brucie began with some helpful hints on deportment for the elderly: "Old people walk like this," said Brucie, shuffling across the screen in a parody of a geriatric dodder. "You've seen them, haven't you? You've seen them everywhere... Now the first thing they should do is raise their diaphragm..." Brucie walked back again, slightly more upright this time. "OK... they still look old..." he said, shuffling back for another pass. "Raise the diaphragm and swing the arms... They still look old, don't they?" He went back to his starting position for the final improvement. "But. The missing link is... move your shoulders with your arms and then you've got someone who is old but he can walk, and he has a rhythm about it." Brucie did a jaunty little stroll and then turned triumphantly to the camera, to make a direct address to his younger viewers. "Do what I've just done and you will solve Not Looking Quite As Old As People Think You Are." Brucie is now 82, an age when most people would assume that they might count as "Them" too, but he appears to feel that time operates differently for him. Asked towards the end of David Nath's film whether he'd given any thought to his funeral arrangements, he replied, entirely without irony: "When it gets near to the time I think I will give it great thought." No immediate rush, obviously.

Another solution to the Not Looking Quite As Old As People Think You Are conundrum is to keep the camera at a respectful distance. As Bruce prepared to run through the "fountain of youth" exercises that his mother-in-law had recommended to him on his wedding day, he gave strict instructions to the director: "By the way, no real close-ups... no real close-ups. Close-up of the toes, but no close-ups of the face. The toes are much younger than the face." Bruce's toes -- which did indeed look surprisingly sprightly – clenched and unclenched in centre frame. Bruce's mother-in-law, incidentally, is younger than he is, which may be why she felt that a rejuvenating exercise programme was a suitable wedding present. For the last 30-odd years, Bruce has been married to Wilnelia, a Puerto Rican former Miss World, who is almost as big a celebrity in her country as Bruce is here. When they spend time in their Puerto Rican home – in a gated community designed to protect the rest of the island from wealthy golfers – he's apparently known as Señor Mundo.

Quite why Forsyth had given access to Nath for this film I don't know, but the result was a gently comic portrait that suggested that his Generation Game persona – fussy, slightly controlling, exasperated that people won't follow his advice – was built on real foundations. The film was a positive blizzard of uninvited advice. In addition to Brucie's posture and exercise tips, we were also given a blow-by-blow account of the Brucie way to prepare breakfast porridge (not forgetting the critical matter of blueberry dispersal in order to avoid unpleasant clumping), advice on washing shirts and socks (don't ball them up because the elastic goes), an itemised account of what you should pack for a day out on the golf course ("Don't get dehydrated... if you get dehydrated, it's really bad"), plus tips for holiday reading (Bruce favours courtroom dramas and directed our attention to Shadow of Power by Steve Martini, "a great writer"). And when he wasn't doing that he was fussing over Nath's camera placements (he was very anxious that we didn't get to see how messy his golf-buggy garage was) and policing his own performance as Bruce Forsyth, national treasure. Whenever he stumbled over a phrase – as we all do in everyday speech – he rewound a few seconds and did a retake, as if he was on a sound stage and the gallery director had just mentioned it over the earpiece.

How Wilnelia puts up with it I can't imagine, but she does, remaining serenely equable through everything, even the irascible little spat Forsyth had with an overzealous security guard in their Puerto Rican resort. Nath did include one mildly snide dig at the nature of their relationship: "What was it Winnie had seen in him beyond the porridge and the socks?" the voiceover asked ingenuously, before the image cut to a long shot of Bruce's Wentworth mansion. But everything you saw on screen suggested that their marriage is a genuinely loving one, not a mid-life crisis for him or a gravy train (or gravy golf-buggy) for her. That's his secret, I think – not diaphragm control or the adrenalin of performance, but marrying someone he urgently wants to stay young for.

Engineers sometimes legitimately complain that television doesn't honour their contribution to the modern world quite enough. Railway enthusiasts can hardly complain, though, since there seems to be a general rule that there must always be at least one presenter riding the rails at any given time. The latest is John Sergeant in Tracks of Empire, a brief history of the Indian railways, an enterprise described by its first mover – Governor General James Broun-Ramsay – as "vastly surpassing in real grandeur the aqueducts of Rome, the pyramids of Egypt, the Great Wall of China and the palaces, temples and mausoleums of the great Moghul monuments". Not always as beautiful, it has to be said, but ask even the most fervent Indian nationalist, "What did the British ever do for us?" and the answer is likely to be the railway.