Fans of the BBC series Sherlock were carrying out detective work in Tenby this week, speculating what scenes were being filmed on historic landmark St Catherine’s Island for the latest season of the award winning show.

There was no sign of main star Benedict Cumberbatch or his Dr Watson sidekick Martin Freeman, but one of his former comedy co-stars from The Office did appear for filming in the form of Ralph Ineson, who played the recurring character Chris Finch in the popular BBC sitcom.

Ralph who will be well used to fanatical film and TV fans having played Dagmer Cleftjaw in the second season of Game of Thrones, and Amycus Carrow, in the Harry Potter film series, was dropped off in Tenby harbour with other cast and crew on Monday afternoon, and after correcting a wrong turn, made his way down Castle Beach to film scenes with a number of extras dressed in black carrying guns around a cove of the island.

Director Benjamin Caron, who recently filmed feature-length episodes of the multi BAFTA and EMMY winning series Wallander starring Kenneth Branagh, was also spotted at the location.

The following day scenes involving a black helicopter circling the island and ‘henchmen’ storming the fort with guns, alongside what appears to be a Moriarty flag flying, has led to speculation on film fan sites that St Catherine’s could be used as a lair by Sherlock’s nemesis.

That area of Tenby is no stranger to a spot of celebrity spotting for filming, as Lexden House in St Julian Street was chosen as the location for the two days’ filming of interiors and sea views, for Dylan Thomas biopic The Edge of Love in 2007, with stars Keira Knightley, Sienna Miller, Cillian Murphy and Matthew Rhys, all in the resort for filming.

Castle Beach was also used in 1997 to shoot scenes featuring Christian Slater and Jared Leto for historical drama Basil.

Pete Prosser of the Tenby Island Project who has re-opened St. Catherine’s Island to the public in recent years, said that this was a “fantastic promotion opportunity” not just for the island, but Tenby particularly and Pembrokeshire.

“The global viewing figures for Sherlock are astronomical, reflected by the 5.5 million following for the series’ official Facebook page,” he said.

“An adaption of the Count Of Monte Cristo was shot on the island in 1964, but nothing as big as this. This will showcase Tenby to the entire world,” added Pete.

Film crew stored equipment and gear at Tenby Sailing Club, whilst a number of vehicles occupied the lower Salterns car park.

Cabinet Member for Transportation and Major Events Councillor Rob Lewis said that Pembrokeshire was delighted to welcome the cast and crew of one of BBC’s “biggest shows” to Pembrokeshire

“Our County always looks good on film and I’ve no doubt the exposure it will receive will boost visitor numbers in the future,” he remarked.

“I’m not sure when it will be shown on TV but I’ll definitely be tuning in to watch. I’m a big fan of the show and it will be interesting to see how St Catherine’s Island will feature in the story,” added Clr. Lewis.

Stars Benedict Cumberbatch and Martin Freeman, recently shot scenes for the second episode of the brand new three-part season 4 series at the Cardiff University Student’s Union.

It is believed that further filming could take place in Tenby next week.