We all enjoy spotting anachronisms in historical drama.

Henry VII wearing the wrong kind of socks, or Julius Caesar looking at his wrist watch.

I gather that even Downton Abbey has continuity cock-ups.

For me, however, the boot is now firmly on the other foot.

I’ve been working as the historical consultant on a new period drama series set in Birmingham and due for screening, I think, next autumn.

I don’t believe I need to keep mum about this anymore, since there’s plenty about it on the net. I just can’t tell you what happens.

If period drama has tended to become fixated with upstairs and downstairs lately, there’s no danger this new series will fall down the same flight of steps.

We’re talking Birmingham in 1919, gang warfare, street crime and hints of revolution.

The series takes its name from the most notorious of the Birmingham gangs of the time. It’s called Peaky Blinders.

All this is quite a challenge. As a historian it’s perfectly possible to shy away from things you don’t know. What colour dress was Elizabeth I wearing when she spoke to her troops at Tilbury? I don’t know.

What did Vasco da Gama have for breakfast? I’ve no idea. Best avoid these things.

Put them onto the small screen, however, and there’s no place to hide. You have to make a decision.

There’s an early scene in Peaky Blinders set in a pub after a Birmingham City home game. The players are there, as they often were in those far-off days, and so are the supporters.

So what colour jersey is the goalkeeper wearing? And how did the fans show which side they followed? Did they wear rosettes or scarves?

Hours of research and agonised reflection followed.

My best guess is that the keeper wore green, and that the supporters had nothing to show they were Blues fans, apart from their accents.

None of the photos of football crowds I unearthed showed a single scarf. They might have had rattles, though. They brought those back from the war.

But I’m afraid that’s as much as I’m telling you so far.

• Dr Chris Upton is wrestling with the past at Newman University College in Birmingham.

>More from the BBC on Peaky Blinders