New Blood, BBC One

New Blood began as it didn’t quite mean to go on. Somewhere in India five Brits on their travels mustered in a medical laboratory as volunteers to test-run a new drug. The tone was pregnant with portent, so it was no surprise when a knife was wielded and blood spattered. You settled in for a moody medical noir.

Six years and one title sequence later, the tone made a 180-degree handbreak turn. Standing over the corpse lying at the foot of a block of flats in rainy London, Mark Addy’s old-school plod (pictured below) spouted sarky putdowns at a uniformed young upstart who fancied himself a detective. The corpse, it turned out, belonged to one of the five guinea pigs we met earlier. By the end of the hour two more had died, one off-screen in a car crash, the second pushed down a long escalator at Canary Wharf. No wonder another of the guinea pigs was a bag of nerves, living at home with his mum and being groomed on Skype by a manipulative temptress calling herself his girlfriend.

The pile-up of bodies has something to do with a pharmaceuticals company neck-deep in a rigged market via which generic drugs are sold to the NHS at inflated prices. Very topical then.

The sleuths unwittingly coming at the case in a pincer movement are both of immigrant stock. Stefan Kowolski (Mark Strepan) is a young pup at the Serious Fraud Office, pretending to be more Polish than he is as an undercover investigator spying on the sleazy chief pharmacist for half a dozen London hospitals. Meanwhile PC Arrash Sayyad (Ben Tavassoli) is a cocky young constable who, granted the chance to prove his mettle as a detective, gets lumped with Addy’s tub-o’-lard DS Derek Sands.

The first episode introduced us to their background (slobby Polish flatmates for Stefan, myriad Iranian aunts for Arrash) before introducing them to each other at a duathlon (this drama makes a play for a niche audience by going big on road bikes) where they arm-wrestled each other into second place.

The script is by Anthony Horowitz, who just about pulls off the shifts between farce and flirtation on the one hand and spooks and menace in the other. Addy is a treat, and Anna Chancellor is as ever delicious playing someone bossy at the SFO. Of the other seniors, Mark Bonnar as another shady government fixer (see also Undercover) should maybe have a word with his agent.

But the strength of the series rests on the chemistry between its two perky leads, the new blood of the double-edged title. New Blood is likeable, stronger so far on plot than personality, longer on energy than plausibility, and not very groundbreaking unless a rare starring role for the SFO counts. If you want to know what happens next – and by the end of episode one you probably do - the BBC is releasing episodes in advance on the iPlayer.

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@JasperRees