To call Ramsey, on the north coast of the Isle of Man, a one-horse town would be inaccurate — the horse has obviously bolted. Yet, just two miles outside this sleepy hollow, there is a surprising amount of security at the start of a rough track leading to what looks like a large cow shed. But this is no shed, this is the Isle of Man film studios and the security is to keep back the Johnny Depp fans hoping for a glimpse of their idol.

The second reason for the security is because, as my taxi driver puts it, “they’ve got 300 naked people in there”.

Depp is currently filming The Libertine on the island, the story of John Wilmot, the 2nd Earl of Rochester. A rake, soldier, poet of the Restoration and leader of the “Merry Gang” at the court of Charles II , Rochester died from syphilis at the age of 33 in 1680. Samuel Johnson summed him up as having “a total disregard to every moral”.

So when the call went out for extras for the film there were many salacious stories about the “partial and total nudity” that would be called for. The casting of these extras was to be handled by an agency run by former Page Three model Nina Carter, which added an extra frisson.

“If everyone was naked,” remarks a dresser during my fitting, “then I would be out of a job.”

“My boyfriend was cast for the nude scene,” confides one girl, “but they kept upping the ante — first they wanted him naked, then to simulate sex with a woman, then to simulate sex with a man.” This may explain why the crew was looking for one more extra for the nude scene. As a common-or-garden extra earns only £65 a day, whereas the disrobed extras would trouser £250, it was definitely something to aim for.

“All hats off,” commanded a member of the production crew, which sounded like a step in the right direction but was only because Charles II was to be bareheaded, so all his subjects must be the same in his presence. So, bareheaded we remained as the hours passed and our place in the food chain became ever more apparent.

A motley selection of retired telecom engineers, taxi drivers, art students, factory workers and the unemployed would routinely stampede to the food truck for their meals of Dickensian slop, while the crew would feast on Barnsley chops with minted new potatoes only 100 yards away.

Time was passed with games of cards, yesterday’s papers, the banal conversation of strangers and simply staring into space.

“Is it true,” inquires a man with an extravagantly hooked nose to an Alan Titchmarsh lookalike who heard about the job on Manx Radio, “that it is the darkest hour before the dawn?” John Malkovich, as well as playing the part of Charles II, is the producer of The Libertine. I do my best to catch his eye. Surely he would detect a suitably debauched quality in my demeanour and pick me from the crowd to take part in Rochester’s orgiastic dream scene. I lounge in as louche a manner as possible, but he remains impassive beneath his wig.

In make-up there is a blackamoor, a dwarf and a dissolute couple with white face paint and heavily rouged cheeks — surely they must be key elements for unseemly cavorts. But no, they are “featured” extras. There is a hierarchy within the cast of extras, from myself to featured extras, to “action” extras, to “dialogue” extras, to the lucky 30 who will earn top whack in the dream scene.

Still with my mind on that £250, I concentrate my resolve. However, it is not easy to convey sexuality at 6.30 in the morning wearing a wig, a battered frock coat and mud-spattered breeches while holding two sausages in a bun.

Nudity is on the cards today. “I’ll brazen my arse,” declaims Johnny. Unfortunately it is not Depp but Johnny Vegas, who is playing the part of a hell-raising nobleman.

The subject of nudity, unsurprisingly, is the main currency of the chatter in the extras’ holding area. The men who are to take part in Rochester’s dream scene mix braggadocio with slight unease. The women who are to take part are remarkably sanguine by contrast. Karen, studying for a PhD in freshwater ecology, is no stranger to being naked in the company of strangers. “I pose for a life-drawing class, so they know I’ve got no problem with nudity — especially not with Johnny Depp.”

What about Johnny Vegas? She performs a comical shiver. And shiver they will, as another squall of wind blows in from the Irish Sea.

In the corner of a wood-panelled room heavy with drapes and gloom is a figure dressed in black. “These are the Tower rooms,” he intones. The keen wind, the memory of Vegas’s mooning, the possibility of unbridled licentiousness in the Tower rooms . . . I make my excuses and leave.