WHAT is it about detective series that makes them so watchable?

Good or bad – and even so-bad-it’s-good – it’s easy to get hooked on the often formulaic plots.

Central to many detective shows – in this case ITV’s Whitechapel – is the partnership between the grisly old school and preppy new boy.

Here we have the delectable ex-Spook Rupert Penry-Jones as OCD DI Chandler and Phil Jones as DS Miles, backed by a team whose real spine is Hannah Walters DC keeping the men in check.

And of course, East Lancashire’s Steve Pemberton in another kooky role as the basement-lurking historian.

Team dynamics aside, the plots are quite frankly on the bonkers side, but I’ve gotten right into all three series, taking in Jack the Ripper and the Krays, and this time a hotch-potch of past murders.

This week’s part one of two was the creepiest yet, and so far I’ve not a clue who the killer could be – unlike the previous series three tales, where familiar actors crop up in single-scene roles far too small for their status in the first hour.

There’s something suspect about the counsellor, and I have an inkling my namesake, booze-loving two-time divorcee DC Mansell could be on to it too.

It may not be a high-class or gritty drama, but it’s gripping non-the-less, and our household will certainly be tuning in to catch the final part on Monday, then waiting with eerily baited breath for the next outing.