I agree that all the Portillo railway journeys are well done: informative, well shot, good research, interviews that don't go on too long. Refreshing to watch a programme that is is done 'straight'; so many programmes now seem to have to have an angle, be tongue-in-cheek, a 'sideways look at', jokey, post-modern, ironic etc etc
I watched him just the once - he was travelling the Metropolitan Line and stopped in Pinner to make cucumber ice cream, and I just thought "what's that got to do with trains?" So I haven't bothered again.