It's 4am in Venice, and Rupert Graves is flying through the canals on a water taxi. He's on his way back to the hotel after a night shoot and there are no other boats – and certainly no tourists – around.

That's the memory the Sherlock star, 57, recalls vividly when asked for his favourite moment from shooting Sky Atlantic series Riviera.

"It was jaw-droppingly beautiful," gushes the actor. "Sitting on set in Venice - which was lit beautifully - in the best clothes I've ever worn in my life, was a real personal highlight."

Graves joins the cast of the thrilling drama for its third series, playing the charismatic and charming Gabriel Hirsch, who starts working with the lead character, Georgina, played by Julia Stiles.

A year has passed since the explosive finale of the second series and, now known as Georgina Ryland, she has abandoned the cursed Riviera and has started her life over again.

"Gabriel offers her a job that proves to be more of an adventure and she can't resist it, so they go off to Venice to recover a stolen Picasso and that's quickly wrapped up into an international conspiracy that takes them to Argentina," teases New Yorker Stiles, 39.

"But first they find themselves back in St Tropez, and Georgina runs headfirst into Nico Eltham and then Daphne Eltham.

"And because that is a very interwoven community of wealthy families that know everything about each other, her plan to get away from her past is going to prove very challenging."

So, what made Graves - also known for films such as Maurice, A Room With A View, and V For Vendetta - want to take on this telly role?

"I'd never seen a show about the super-wealthy, that was done in this way, which I found interesting because I found it dreamy and quite hallucinogenic and... not aspirational, but if you aspire to be like these people, good luck to you!

"I found it dysfunctional and interesting. And I found the mystery of who Georgina is, and why she does what she does, really, really involving. So yeah, it was that really - and getting to work with Julia too."

Stiles notes there are certainly a lot more shows on our screens now that are "female-driven, or at least with female main characters", compared to when she started out acting, aged 12.

"I remember when I signed on for the first season of Riviera, I thought, 'Hmmm this is interesting' because there was Irina, who was the matriarch, and then there was Adriana, the younger ingenue, and I felt I fell sort of in the middle," continues the actress, who is best known for teen favourite films, 10 Things I Hate About You and Save The Last Dance.

"I thought 'OK, as the lead, they're not going to know what to do with me, because I'm in between the sex object and the maternal character', which are previously normal tropes for a female character. And I've been so pleasantly surprised at how rich and intriguing Georgina has become as a character.

"And so, I'm pleasantly surprised that I've had the opportunity to work on a show where I play a character that is really surprising and reckless and doesn't make the right decisions all the time. It's been very rewarding."

Riviera returns to Sky Atlantic on Thursday, October 15.