Lamb, the dishevelled, flatulent, acid-tongued boss of the titular band of MI5 screw-ups and losers who have been banished to a life of pen-pushing drudgery in the purgatory of Slough House, is a peach of a part.

Physically, Oldman doesn’t resemble the Lamb of Mick Herron’s Slough House novels, who’s described as looking “like Timothy Spall gone to seed” (written before Spall’s weight loss), but he brings the character to life so sparklingly that it’s impossible to imagine anyone else as him.

Whether waking himself from a nap with the ferocity of his own farts, giving his hapless charges the opposite of a pep talk (“You’re useless, the lot of you. Working with you has been the lowest point in a disappointing career”) or – in the later episodes – getting to demonstrate his true mastery of spycraft by outfoxing devious MI5 second-in-command Diana Taverner (Kirstin Scott Thomas), Lamb is a character for the ages.

Balancing thrills, laughs and well-rounded characters is a supremely tricky high-wire act. Slow Horses, which upended the conventions of the spy thriller while also being a cracking spy thriller in its own right, pulled it off brilliantly, particularly in last Friday’s terrific finale.

Despite Lamb ordering the Horses to keep their heads down and try not to get killed by Taverner’s ‘dogs’ – witheringly, he told them they would be lucky to survive half-an-hour – they insisted on doing the opposite by setting out to rescue the kidnapped Hassan (Antonio Aakeel) from his white supremacist abductors, the Sons of Albion, who intended to execute him.

The kidnapping was, of course, a false flag operation set up by Taverner, who had had an agent infiltrate the group. The plan was for Taverner’s team to heroically rescue Hassan, thus putting her in the good books with her boss, Tierney (Sophie Okonedo).

But everything went belly-up when one of the kidnappers, a nutter called Curley (Brian Vernel), sniffed out the agent and chopped his head off.

Standish (Saskia Reeves) and obnoxious tech wizard Ho (Christopher Chung) managed to track the exact whereabouts of the van being used to speed Hassan to his death.

Louisa (Rosalind Eleazar) and Min (Dustin Demri-Burns) galloped off in hot pursuit – and promptly ran out of petrol on a lonely road.

With typical incompetence, Min had been too busy thinking about food and the possibility of having sex with Louisa to bother filling the tank.

Luckily, Lamb and River Cartwright (Jack Lowden) were behind them in another car. The four eventually caught up with the van.

River – a highly competent young agent who had only landed in Slough House because he was stitched up by a jealous colleague – had a Bond-style shootout with Curley, who by now had killed his two accomplices, but it was Hassan who disabled him with a well-aimed rock to the head.

Back at Slough House, celebrations were cut short by Lamb, who delighted in reminding his motley crew they hadn’t actually saved anyone.

Hassan saved himself by turning the kidnappers against one another and then felling Curley.

Still, at least the Horses achieved something. As helicopters and ‘dogs’ swarmed everywhere, they formed a human shield around Curley, meaning Taverner couldn’t cover up the mess she had made by having her men pick him off.

Not that it made any difference. Fearing a scandal, Tierney was happy to sweep the whole thing under the carpet and forget about it.

But that wasn’t the end. A flashback to a shocking act of violence by Lamb when he was a field agent under the command of River’s grandfather, retired MI5 legend David Cartwright (Jonathan Pryce), tantalisingly sets things up for season two.

There are eight books in Herron’s series. I’ll be happy, too, if Oldman goes on playing Jackson Lamb for years to come.