For anyone interested in roads, how the motorway network of Britain was built etc, I watched the whole thing today and have to say it is a really excellent watch imho.
Its available on the BBC iPlayer, but only for a few more days.
Its in 3 parts, each one is an hour long:
Part 1 - Falling In Love
Part 2 - The Honeymoon Period
Part 3 - The End Of The Affair
Quality BBC Four documentary, only on BBC iPlayer at present though, it must have been on television last week. I didnt even know about it until the other day when I was on the iPlayer listings lol.