11 fascinating facts you might not know about Death in Paradise

1. Harry the Lizard may be immortal. Because although Harry is at least 10 years old now – far beyond his expected lifespan – he is considered absolutely integral to the show. "Will Harry the lizard ever die? We talk about that sometimes," says Key. "That would be a good story, the death of Harry, but I think there’d be an outcry. I think the viewers would be furious." He adds: "I worry that he’s a bit like the ravens at the Tower, you know?" So – Harry can never be killed off, or we're all doomed.

2. Death in Paradise originally had a different theme tune in France. Instead of the Death in Paradise theme song most of us associate so strongly with the show (a cover of You're Wondering Now, arranged by Magnus Fiennes), the first few seasons of the French version of Death in Paradise had Sunday Shining by Finlay Quaye as the theme tune.

3. All the equipment used to make the show once got stuck at sea on the way to Guadeloupe. In the early years of Death in Paradise, there was very little filming infrastructure on the island, so everything had to be shipped out there for the production to use – including an electrical generator. And before filming for series two, everything went wrong. Key recalls: "The boat broke down in the middle of the Atlantic, and it sat still in the middle of the Atlantic for about three weeks. There was a tracker where you could see where the boat was, this huge shipping container, and it wasn’t moving. The start of the shoot was approaching. And – it was the generator. It was cabling. It was lights. It was the dolly. I think there might have been a costume truck on it.

"And when it finally arrived – which was, I think, a week into the shoot, and we’d had to busk it for the first week – there was then a strike at the port in Guadeloupe, so the shipping container arrived, but we weren’t allowed to get on it to take anything off. You could literally see the ship but you couldn’t get to it to take the stuff off. And then when we did get on it to take the stuff off, somewhere in transit, someone had broken into it and stolen all the cabling. It was one thing after another."

4. The shack on the beach now has to be protected from partygoers. The DI's rustic home on the beach gets put up and taken down for each season, and packed away into storage until Death in Paradise returns. But in recent years they've had to go further and fence the whole thing off. Key explains: "We’ve had years where we’ve left it to the elements, and then people were having parties in it at weekends, like tourists having parties. We were like, 'We have to secure this a little bit more now.'"

5. DI Neville Parker actor Ralf Little guest starred as someone else in in series two – but that didn't matter. The show's current lead actor appeared in a 2013 episode as a character called "Will Teague", but enough time was judged to have passed so that it wouldn't be jarring for viewers. Key says: "You have a system with rules. We never reuse the same location, and we never reuse the same guest actors, and all that sort of thing. But the longer the show goes on, the more you have to look at your rules and interrogate them. If you believe that the person is right for the role, the fact he was in one episode in series two didn’t seem that big an impediment. I think if he’d been in an episode the year before, that might have been trickier."

6. Sara Martins broke her leg during filming for series one, although it was successfully kept hidden on screen. Thorogood recalls getting a phone call with the bad news: "For starters, she couldn't be in episode five at all, because she’d broken her leg and was in hospital. We’d also written out Richard Poole in that episode so that Ben could come home and have a bit of a break. So there was neither Ben nor Sara.

"Then for the rest of the series, we could write her, as long as she never walked or moved in any way. So in episodes six through eight of series one, you only ever see Sara lift herself up or down into or out of a chair. And if you ever see her walking, it’s a wide shot, and it’s a double." Sara Martins' character DS Camille Bordey also suddenly discovered a passion for wide-legged cargo trousers, as can be seen in some of the promo pics for the series.

7. Another fun fact about how Harry the lizard is filmed using CGI: during filming, the team uses a little model or a reflective silver ball as a stand-in – and the actor just has to use their imagination. Key says: "There’s this thing they have to do where you put this silver ball on set, and it reflects the light. You get an image of it that the computer geniuses can kind of work out where the light’s coming from, and where the shadow would fall, and all that kind of thing... and Kris [Humphries] was very proud of having a thing where there was a little air thing under his shirt, so they could make it look like Harry had just landed on him and walked across." He adds: "The company that do him for us are brilliant, and have got his mannerisms just right. But there were times in the earlier days where you’d look at it, and you’d go, 'He’s too sentient, isn’t he?'"

8. Fans still send angry messages about DI Richard Poole's death. Key tells us: "They were traumatised by the murder of Richard, and I still get messages on Twitter to this day from people who are quite angry that they’ve just discovered the show, fallen in love with Richard Poole, and then discovered him with an ice pick through his heart."

9. There are four Death in Paradise spin-off novels – but there probably won't be a fifth. Robert Thorogood, who created the show and writes many of the episodes, used the show's original characters to write the Richard Poole Murder Mystery novels: A Meditation on Murder (2015), The Killing of Polly Carter (2015), Death Knocks Twice (2017) and Murder in the Caribbean (2018). He explains: "The last Richard Poole novel I wrote, which was three or four years ago now, I found I was really struggling to remember the version of Death in Paradise that predates Kris [Humphries], that predates Ardal [O'Hanlon], that predates Ralf [Little]. The show is now subtly so very different from series one and series two that it seemed to be more dimly graspable by me. And I found it quite a struggle."

Also, the idea of writing extra spin-off novels starring one of the show's later detectives is a no-go, because whoever didn't get chosen would be mightily offended. Thorogood says: "I was able to go to the Christmas party, and when Kris said, 'I hear you’re doing a murder-mystery series with Ben bloody Miller', I was able to say, 'Ah, yes, but Kris, he’s the original detective, so that’s why I’ve done it...' I think my ability to talk to all of the actors who’ve worked on the show – the only satisfying answer is: it’s the original cast. Anything else, I’d get cut dead."

10. The French actors in the show do the French dubbing. Which means that Joséphine Jobert (DS Florence Cassell) and Elizabeth Bourgine (Catherine Bordey), who are native French speakers, have to perform their scenes in English – and then, in post-production, they voice their own lines in French. But because it's a dub, the lip movements never quite match up. Other voice actors are, of course, brought in to do the dubbing for the non-French-speaking actors.

11. Catherine's Bar is a real place, "although it’s run by a slightly grumpy woman who I think resents having so many tourists come and drink there," Thorogood says. "Because the last time I was there just to have a cup of coffee, I think she rolled her eyes, that we were about the 400th-billionth person to turn up just for a very cheap cup of coffee." But, he adds, "It’s an amazing spot. What’s extraordinary about it is, you sit there, and it’s Catherine’s bar. You can’t believe you’re on a film set, because that is the view. You get real goose bumps."

The Death in Paradise double bill airs on Thursday 4th and Friday 5th February at 9pm, with season 10 then continuing on Thursdays. Check out what else is on with our TV guide.