Now here’s a warning from history.

If nothing else, these platform signs at Moorgate are a testy reminder of the perils of a rebrand. The red diamond, had it been given the chance, might have persisted long enough to become stoically tolerated, then grudgingly accepted, then maybe even loved.

But it was doomed, and all thanks to bad timing. The diamond came too late. The roundel had already been conceived. Red discs were arcing out majestically across London when the Metropolitan line, as stubborn as ever, decided to launch its own logo. And worse, it was a logo similar enough to the roundel to make the Met’s behaviour look incredibly petty.

Which of course it was. Mere pettiness never stopped the Met doing anything. But as an exercise in brand awareness, let alone one of design aesthetics, it was amusingly hopeless.

The signs* make Moorgate station a wonderfully eerie if slightly creepy place. For they appear on platforms no longer used by trains, save the occasional service that needs to terminate here.

Yet the platforms don’t look abandoned. Far from it. They feel clean, attended, cared-for. It’s almost as if they were in constant use. But by whom?

There are no security barriers. The platforms are teasingly, tantalisingly, open to anyone. I doubt you’d be able to stroll very far before being stopped… but the temptation is there. As is the potential for misunderstanding. I saw one family start to walk along them, before realising their mistake. I kind of wish they’d have carried on, just to see what happened.

I realise I like these platforms for the wrong reasons – there’s very little logic in loving something that is useless – but they don’t quite sit abandoned in splendid isolation.

Platforms five and six (above) might be completely cut off for trains (they used to be the terminus for Thameslink services) but they’ve taken on a new life as a sort of promotional space-cum-display area. At the time of writing they’re hosting a rather nice mural celebrating the Underground’s 150th anniversary. I hope there are plans for other displays in the future.

Platforms three and four are where you’ll find the diamond signs, casting their spiky glare. And both these and the mural are clearly visible from the Circle, Metropolitan and Hammersmith & City trains that call at platforms one and two. So rather than the old bits of Moorgate getting hidden from view and left to rot, they’ve become a “new” feature of the station: a partially-palatable slice of the past for digestion both now and into the future.

And there’s much to digest. But I’ll think I’ll pass on those diamonds. They’re just not my type(face).

*Cheers to Andrew (in the comments below) for noting that the signs were reintroduced for the 150th anniversary. Will they, along with the mural, survive beyond 2013?