The actor starred as DI Humphrey Goodman in four seasons of Caribbean-set murder mystery Death In Paradise, but left the role in 2017 and is now set to pick up Humphrey again six years on for spin-off series Beyond Paradise.
Read more: Who's in the Beyond Paradise cast?
It follows Humphrey's life back in the UK with Martha Lloyd (Sally Bretton), who he originally met in a holiday romance while working in the Caribbean but decided to return to England for.
Marshall has said that despite six years away from his character, he has found picking up where he left off "easy and comfortable".
Asked how it was returning to Humphrey, he said: "Really easy, actually. It's like slipping on an old pair of slippers. He’s a comfortable, lovely old friend - it’s just delightful to play him again."
Although fans of Death In Paradise, which continued on with Ardal O'Hanlon and then Ralf Little in the main role, might recognised similarities in the spin-off show, Marshall explained that Beyond Paradise would be "a different kind of paradise".
The series is set in Devon and Cornwall, where Humphrey has transferred to from the Met for a quieter life in Martha's home town, but he soon finds there is still plenty of crime to tackle.
Marshall said: "Beyond Paradise has the same sort of structure as Death in Paradise, but we're also a completely new show.
"There’s some of the favourite characters from Death in Paradise, but with a whole new spin on it. It's still paradise, it's just a different kind of paradise."
He added: "It's a really unique show. I don't think it's a show that's been done before in terms of the way we shoot.
"Without giving too much away, the way we shoot the denouements and how we solve the crime is completely unique. There are a lot of laughs and there is lot of fun in the show, but I think it's also very thought provoking. We're maintaining that sunny disposition."
Beyond Paradise begins on Friday, 24 February on BBC One.