The hardy men of the Bow Street Runners were used to working alone and thus relied on a loud voice to raise the hue and cry, alert the populace and, occasionally, scream with pain as they were savagely beaten by a criminal gang. The new men of Peel’s innovative civilian police force were, in contrast, equipped with the latest in communications gear – the hand rattle. A Peeler could summon aid by shaking his rattle while in hot pursuit of a felon and hoping that people would stop laughing long enough to help. The rattle was soon superseded by the whistle, whose principal advantage was that, not only could you have a number of prearranged signals for a variety of situations, but you didn’t look like a total tit using it.

Once the telephone had been invented, it was only a matter of time before the police got in on the new technology and, first in Glasgow and then in London, the police box was born. Here a police officer in need of assistance could find a telephone link to Scotland Yard, a dry space to do ‘paperwork’ and, in certain extreme cases, a life of adventure through space and time.

Finally, radios got small enough that a constable on the beat could carry one on his person, call in back-up, report crimes and lie about how long he was taking on refs. Then we got Airwaves, which could be integrated with every other emergency service network all over the country – now a copper under threat can get help anywhere from anyone. There’s even a panic button that opens your mic and broadcasts everything it picks up over the emergency channel. It’s the sort of thing that saves the lives and, even more frequently, the tender parts of police officers.

But then along comes magic, and suddenly we’re supposed to go back to rattles and whistles. Not this PC – I like my tender parts abrasion free.

So I invented the screamer, patent pending. Built around the guts of a disposable mobile phone, it has a felt cover for grip and is weighted for throwing. It’s got a recessed hook slide – you thumb it sideways and release and a clockwork timer starts. Then you throw the bloody thing as far as you can, hopefully outside the area of immediate magical effect, where two minutes later it basically phones the Met control room and screams help, help, serious magic shenanigans here – send help – preferably Nightingale.

I have a guy in Leominster who makes them for me, although he still thinks I’m using them to track UFOs.