Last Night's TV: Billy Connolly's Route 66/ITV1<br />Time Shift: The Picture Postcard World of Nigel Walmsley/BBC4

I'm not sure that it's a good idea to let Billy Connolly do pieces to camera while he's driving. He amuses himself so much that he can be a risk to other road users. He nearly swerved off the road entirely at one point in Billy Connolly's Route 66, while telling us about an enterprising brothel owner who had set up his establishment in a railcar on a stretch of track crossing a county line. When the police arrived from one direction the customers would pile out and push the whole thing into another jurisdiction. "I LOVE that!" roared Connolly, getting the giggles so badly at the idea of all the "bare-assed" customers that his three-wheeler began to drift dangerously towards the verge.

He loves a lot of things does Billy, which, along with the unbridled pleasure at his own jokes, could easily be a bit off-putting. Indiscriminate enthusiasm and comic self-regard aren't always winning characteristics. Somehow, though, he gets away with it. I suppose it's partly because the enthusiasm, though very broadly spread, is spiked with an equally vigorous distaste. Donald Trump was at the receiving end in last night's programme for an act of architectural vandalism in Chicago. "C'mere and I'll show you where that bugger spoiled it," said Billy, who has a very chummy way with the lens (largely, I suspect, because he disregards all those old nostrums about imagining your old mum at home and simply talks to the crew). He pointed to one of Trump's multi-story gewgaws and scowled. "He wants to be the president! Place would be a toilet if he became the president".

As itineraries go, Route 66 provides a pretty good one – slicing through the heartland of a certain kind of Americana stuffed with kitsch roadsigns (there are a lot of plaster giants) and the residues of recent history, including prohibition and segregation. Before setting off, Connolly met a Chicago artist who told him about The Negro Travelers' Green Book, a segregation-era travel guide that told African-Americans where they were permitted to eat and stay and the best places to avoid if the didn't want to get lynched. Once on the road, he mixed standard tourist must-sees (Abe Lincoln's house in Springfield, with its migraine-inducing wallpaper and three-seater outhouse) and slightly less predictable diversions, to chat to an Amish farmer and to cruise through a suburb recently wrecked by a tornado. And then he turned to the camera and concluded in Biblical style, after a quick précis of next week's attractions: "And you shall come with me and you shall be the better for it." Well, certainly no worse, which is more than you can say for a lot of programmes.

Ambition should be rewarded, and particularly the ambition to make documentaries in inventive ways. Unfortunately, one of the reasons ambition isn't more widespread is because it's risky, as was neatly demonstrated by Time Shift: The Picture Postcard World of Nigel Walmsley. Rather than do a conventional BBC4 enthusiast's guide, Gerry Dawson had framed his film about the history of postcards (and how deliciously BBC4 is that?) as a kind of fiction, in which an unseen character called Nigel Walmsley was mistakenly invited to give a talk to a men's club on the subject and decided to do it anyway to collect the fee. As he bones up on his subject, we see things entirely from his point of view (including a glass of wine lifted to the camera lens).

The first mistake was to get Christopher Douglas to play Nigel, not because he was bad but because he has a distinctive voice that many viewers would associate with Ed Reardon, the misanthropic (and very funny) hack from the Radio 4 comedy. You hoped that Nigel would just be Ed by another name – splenetic and reactionary and rude – but he couldn't be because he was too busy doing polite, functional stuff, like introducing clips and interviews. Unfortunately, having once been taken up the conceit couldn't be dropped, however awkwardly it got in the way of what would otherwise have been a perfectly entertaining miscellany of postcard history and aesthetics. Still, some of it was fascinating. With seven postal collections a day, it was quite possible to use a postcard to arrange an evening date with someone in the same city. And postcards of local news events, a big seller, were produced with remarkable speed. A postcard about one Croydon train crash, which occurred in the morning, carried an 8.30pm postmark from the same day, the card having been printed and distributed in just a few hours. Not quite instant-messaging but close.

t.sutcliffe@independent.co.uk