A few new quirks and no jacket, yet Death in Paradise slips seamlessly from Kris Marshall to Ardal O'Hanlon

Ardal slots straight in to Kris's place in the trailer, which is the first clue that Saint Marie's latest Detective Inspector is cut from the same cloth as Goodman (even if that cloth isn't linen).

Strictly speaking, Mooney isn't the resident cop just yet – or at least, he is, but he doesn't know it.

Along with his daughter Siobhan, he thinks he's just on a nice Caribbean island for a working holiday, staying in a beach hut leant to him by his new buddy Goodman.

But even though he thinks he's on holiday, Irish copper Mooney jumps at the chance to bring out his short-sleeved shirt and tie (something Kris Marshall wasn't too impressed by) and get stuck into a murder investigation. The only twist is that the killing actually happened eight years ago, and new evidence suggests the wrong person was convicted.

So, what to make of Mooney?

The first thing that strikes you is the sense of continuity. Mooney's dialogue is pretty much exactly like Goodman's, and (as we glimpsed when the two worked together in London) so is his approach to investigating a crime. He's instantly at ease in the office, but he also leaves Florence, JP and Dwayne perplexed by his sudden unexplained brainwaves. In short, it's just like the old days.

But his first solo episode does reveal some new quirks – which is exactly what we need to establish a new character.

We see that he likes to act things out (hence the finger-gun! pew pew pew), he talks to himself, and he's more of a comic character than Goodman ever was. As we saw in the London episodes, he also has a tendency to chatter and come across a bit odd, like his Father Ted character.

"I suppose, with me, they’re going for something a little bit quirky on the island,” he previously told Radio Times in an interview. “I’ve tried to bring a certain kind of a warmth to it. Mooney is quite friendly, quite genial and slightly underestimated because of it. Maybe there’s some of the naivety that I’ve brought to other characters before.”

Mooney also brings some baggage with him from London, which sets up lots of potential for storylines: he has a beautiful daughter in her early 20s, he's a recent widower, and he's still grieving for the wife he adored.

But honestly, it's a relief to find that very little else will change in Death in Paradise, despite the Doctor Who-style Inspector regeneration.

The BBC1 comedy drama may be formulaic, but that's all part of its charm. Every week you get a murder (nothing too gory, that would ruin the fun), a bunch of suspects, a few false leads and a puzzle, until the DI suddenly has a flash of insight – and gathers everybody together to explain exactly how the murder went down. Mess too much with the basic formula and you'll have some very grumpy fans, so the introduction of Mooney had to go seamlessly.

The verdict? It may be sad to say goodbye to fan favourite Kris Marshall after four years, but Ardal O'Hanlon will make an excellent head cop on Saint Marie, even without the jacket.