Both the coolest and most troubled maverick detective on British television was back in Luther.

A gripping one-off two-part special found DCI John Luther pitting his wits against yet another freakishly ingenious serial killer – a computer whiz who also happened to be a cannibal. Not a good combination.

His return represented something of a mixed blessing though.

On the one hand it was good news for fans of Idris Elba (i.e. all of us).

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He's back! A gripping one-off two-part special found Idris Elba's DCI John Luther pitting his wits against yet another freakishly ingenious serial killer – a computer whiz who also happened to be a cannibal

On the other, the storyline and style of the show left viewers with a more vivid imagination risking a sleepless night afterwards, wondering if they had just heard a strange noise imagine downstairs or there really was someone creeping around about to open the bedroom door (all of us again).

Your heart went out to anyone watching who was home alone, about to do the late shift in an office, or working for the London Tourist Board.

Images of the city's shiny attractions have become obligatory in modern dramas these days but here were restricted to one distant shot of the Gherkin. Instead they were replaced by a grim, grimy, gory, urban wasteland beset with a techno weirdo spying on us in our homes and nutters emailing fetish websites with names like Cannibal Erotica.

'They were exchanging intensely detailed fantasises about how they wanted to kidnap, rape and cook and eat young women and teenagers,' as one cop said.

All blood and gore: Viewers of the BBC show might be left having a sleepless night due to the chilling events of Luther's comeback episode

'What did he do with the heart?' DCI Theo Bloom asked, arriving at one spectacularly bloody crime scene.

'He ate it,' his boss said simply. Gulp.

Luther was like a less glossy, less glamorous version of Hannibal – the UK version – with elements of another Gillian Anderson thriller The Fall thrown in.

The way the killer phoned one victim's mother was particularly unpleasant.

'I was with him when he died,' he told her chillingly. 'He was asking for you at the end, when he couldn't fight anymore. 'Mum, mum...' He was so scared of dying.'

To quote Crimewatch, don't have nightmares…

No wonder they called in Luther. His old boss brought back him from the 'leave of absence' enforced after his previous case in which the charming, shambling, detective had become involved with Alice Morgan, a seductive psychopath. Well we've all done it…

Nice jacket: Idris returned with a new tweed jacket, after his famous one was seen floating through the air into the Thames at the end of the last series over two years ago

The odd chewed up heart apart, it was fantastic to see him and, after nearly two and a half years, a big surprise.

The last series had ended with Luther's famous tweed coat floating through the air into the Thames, having been thrown from Southwark Bridge (by Alice). It seemed to symbolise Luther's farewell – given that Luther's relationship with Alice had left his job rather untenable and Idris Elba was off to conquer Hollywood in Mandela, Pacific Rim, and Avengers: Age Of Ultron.

Alice and Luther had been planning to run away together to Mexico or Sao Paolo but the opening showed Luther was alone and had only made it as far as somewhere that looked suspiciously like Broadchurch.

We discovered that these days he was living on the coast somewhere, spending his days standing outside his cliff-top cottage perilously close to the edge, looking moodily at the sea. Well it's good to have a hobby…

'What did they do with the heart?' DCI Theo Bloom was forced to ask the most grotesque question of the episode

This had replaced his penchant for gazing over the city from the top of London's skyscrapers.

'Do you ever do this?' we saw him ask DS Justin Ripley in a flashback. 'Come up to a really high place, and wonder what it would be like to fall?'

Happy, happy, happy…Luther always was a gloomy sod, world-weary even compared to his fellow TV detectives. Mind you, he had plenty to be miserable about. Ripley had died in his arms, as did Luther's beloved wife Zoe – both shot having been caught up in the chaos of Luther's investigations.

He was that sort of cop – one who, as his superiors were forever pointing out, attracted Trouble, especially for those closest to him. Simply being on the phone with Luther even before he had officially returned to the squad was enough to seal DCI Bloom's demise - blown to smithereens as Luther responded to his friend's request for help by giving him his insights into the cannibal. That'll teach him…

Luther was then paired up with Bloom's partner DS Emma Lane (played by Rose Leslie – Igritte from Game Of Thrones). Given Luther' track record, you fear for her safety and her future.

One to remember: Luther was like a less glossy, less glamorous version of Hannibal – the UK version – with elements of another Gillian Anderson thriller The Fall thrown in

Good luck: Luther was paired up with Bloom's partner DS Emma Lane (played by Rose Leslie). Given Luther's track record, you fear for her safety and her future...

Earlier Bloom had visited Luther's clifftop gaff to ask him about Alice.

'Pretty close to the edge!' he had cried.

'Closer and closer every day,' Luther muttered. This (in case we hadn't got the message) was how he liked it.

The mystery of Luther's new coat was quickly solved. It was not a coat it was a PARKA. But otherwise Luther was the same - a big bear of a man; a Cockney Columbo; his taciturn macho mumble, stylish stubble, and shambling manner remained.

Alice though was dead, at least according to Interpol. She had been seen in Berlin, Madrid, and Antwerp where she had drowned, said Bloom, showing him a photograph of a body in the water.

'No she's not,' shrugged Luther, stunned. 'It looks like her but it's not her.'

Bloom explained that the autopsy had confirmed her identity from prints and dental records.

'You and Alice Morgan, I'm aware that there was a fondness between you,' Bloom mooted.

'Yeah there was - a fondness,' Luther mumbled.

'Hey are you OK, really?'

New blood: The new episode included Laura Haddock, in the role of Megan Cantor

'Yeah, everything's tickety-boo,' Luther growled. 'Totally disco.'

Of course, it was anything but.

'He was crushed,' Bloom told his boss.

Not quite totally. John Luther was not just any maverick cop. As their old boss had warned: 'the man is nitro-glycerine!'

John Luther gave Idris Elba plenty of opportunities to demonstrate why he would be perfect as the next Bond – rougher round the edges, but charming and certainly tough enough.

'Is he having a laugh?' Luther scoffed when a heavy in one of the more salubrious drinking haunts on Luther's old manner pointed a gun in his face after Luther fired up the Volvo and charged back into London, solving the mystery of Alice's death where his colleagues and Interpol couldn't almost instantly.

Nice to have a hobby...: We discovered that these days he was living on the coast somewhere, spending his days standing outside his cliff-top cottage perilously close to the edge, looking moodily at the sea

When he discovered a contract had put out on Alice by 'an old school geezer from Islington', a crime boss called George Cornelius (Patrick Malahide, who has previous associating with such types from his days in The Sweeney), Luther took direct action. He knocked on his front door and head-butted his son when he threatened to brain him with a golf club and bundled Cornelius senior into the boot of the Volvo, before handcuffing him to a radiator.

As he didn't have enough on his plate with this and Alice, Luther was called away and brought into the team hunting for the serial killer when Bloom was blown up.

Back in the job, to investigate the case, wearing the parka clearly wouldn't have been or looked right. Thankfully he got changed first, strolling in the squad room to the sound of superhero music, wearing the Luther Look – the pre-requisite jacket, shirt, tie, and most importantly of all A NEW TWEED COAT.

With the Volvo and the tweed coat back in situ, the killer now had no chance you thought, especially when Luther reaffirmed his credentials as a reckless Rogue Cop by going into the cannibal's flat, ignoring orders to wait for back-up from the bomb squad.

But Luther's best endeavours were undone when, as is traditional, he and the other cops contrived to let the killer get away – to fight, and eat, and terrify us, in Part Two next week.