Whenever we’re in London for our regular rendezvous with nearest and dearest, we try to fit in something a little different. And what could be more different than riding the Mail Rail? Back in the day when people still wrote actual letters, traffic gridlock in the smoky city was holding up the King’s mail. It just wasn’t on. The solution? Build a mini railway beneath the congested streets. From 1927, the underground mail train ran from Paddington in the west to Whitechapel in the east before hitting the buffers in 2003.

But that wasn’t the end of the line. Some bright spark at Royal Mail saw an opportunity to make a few bob, and Mail Rail opened in 2017 as a visitor attraction. We thought we’d give it a whirl. As we rattled along the narrow tunnel in the toy town choo-choo, the old subterranean world of the postie was revealed with fascinating audio-visual displays projected onto the curved walls of long-abandoned platforms. Then, quite suddenly, we shuddered to a halt and were plunged into total darkness. ‘Attention! Attention! Power cut!’ bellowed a fella with a Cockney accent over the tannoy. Liam looked worried. ‘Only joking!’ It’s not a trip for the claustrophobic – or the long-legged.

Although I’m way too long in the tooth to have been a fan of Postman Pat, that evergreen kiddies cartoon from the eighties, the entire experience brought out the inner child (or geek) in me.