Well, it could be Caribbean or it could be Arctic,” chuckles Graham Campbell down the phone from Inverness. I’ve asked what the weather will be like for my trip to the Western Isles with Britain’s only full-time mobile cinema, and its development manager is sitting on the fence with glee. It’s both T-shirts and fleeces in the rucksack, then.

Nestled in the top left-hand corner of the weather map, the Western Isles, which cover an area of more than 1,000 square miles, are one of Europe’s most remote regions. They have rain, sheep and pristine sandy beaches by the bucketload, but only one permanent cinema.

Which is where the Screen Machine comes in. Built by a specialist company in France, the world leaders in mobile cinema, this £500,000, 55ft (17m) ten-wheeled behemoth can transform in just over an hour into a fully functioning, 80-seat cinema, complete with 13ft screen, Dolby 5.1 sound and even Pearl & Dean advertisements. Every seven weeks it makes a full circuit of the region, stopping at 22 locations, from Lewis in the north to Islay in the south, and showing recent releases to people who are often several hours away from their nearest picture house.

Many are also fervent Christians – ferries have only recently started running on the Sabbath – so Campbell does not schedule screenings for Sundays. But the Screen Machine, which sells up to 25,000 tickets a year, is “a cultural entitlement”, he insists. “There’s not a lot of times when large sections of a village come together.” Before the first machine (this is mark II) began doing its rounds in 1998, “virtually every kid under 10 had never been to a cinema before. They were just wide-eyed.”

Audiences have become more demanding, however. “They can be as disappointed as anyone else if it’s a shite show,” Campbell says. “Which is why we have to have such a good set-up.”

What’s most impressive is that this labyrinth of gadgetry is operated by one man. Neil Macdonald’s job is the epitome of multiskilling: as well as driving this unwieldy beast along miles of winding roads and overseeing its conversion into a picture palace, he acts as mechanic, electrician, ticket seller, projectionist, bookkeeper, cleaner and – if those who can’t get into a show get rowdy – even bouncer.

“Aye, it’s an interesting job,” deadpans the unassuming 54-year-old when he meets me at the port of Ullapool, from where we will board the ferry to Stornaway on the isle of Lewis. Macdonald has been doing the job for three years, and shares it with another operator – each works a fortnight on, a fortnight off. “My wife prefers me not to be away for half a year,” he admits. “When I get back she’s always got a long list of things for me to do.”

The sun is out as Macdonald squeezes the truck on to the Stornaway ferry. Conditions are usually a lot worse, he assures me: “We’ve not had weather like this for six months. Reversing a 55ft mobile cinema on to a ferry at night in the teeth of a howling gale is really quite tricky.”

After a voyage through dramatic, Scandinavian-style seascapes, we land at Lewis and make our way 40 miles south to our first stop: Tarbert on the neighbouring isle of Harris. Lying between bracken-brown hillsides dotted with gorse bushes and clumps of spring daffodils, it’s a sleepy village with a harbour full of bobbing fishing boats.

John Morrison, proprietor of Morrison’s Newsagent’s and Grocers, has already been online to book tickets for The Other Boleyn Girl.

“When you’re living on a remote island like this, it’s a great experience to take your family out to a lovely Screen Machine,” he beams. An older villager, who refuses to be named, is more circumspect, and would never consider going to the pictures on a Sunday: “Och no!” he scowls from beneath his peaked cap. “I’m in church then.”

Macdonald sets up the machine in the village car park – it doesn’t have its own toilets or sell food so it must be parked near local amenities. “The shopkeepers’ eyes light up when they see us because they sell lots of cinema food,” he smiles. “A lot of which ends up on the floor and has to be cleared up by me.”

Once the machine is parked and stabilised with hydraulic legs, it’s time for the fun bit. Macdonald jabs on a Play-Station-style joystick, the outer walls of the trailer flip up and each side slowly concertinas outwards. With the addition of steps and a safety ramp, the metamorphosis is complete. “We didn’t show Transformers last summer,” Macdonald chuckles. “But it would have been very appropriate.” Inside, the effect is Tardis-like: with three blocks of fixed seats divided by two aisles, it feels like being in one of the smaller screens of a normal multiplex.

Macdonald operates the projector in a booth at the back, which also contains a ticket printer, a microwave in which to cook his tea and a small window, “so I can keep an eye on the back row”. The Screen Machine shows three films on each tour, usually the kind of mainstream flicks that put bums on seats and appeal to its core audiences of women and children. As Campbell puts it: “Islanders don’t want to come out questioning their place in the world, they want to have a good time.”

The first film of the day is certainly a Tarbert crowd-pleaser: The Waterhorse: Legend of the Deep, in which a Scottish lad befriends the Loch Ness monster. A scene in which one of the heroes berates an English adversary and his “Sas-senach ways” gets a huge roar of applause.

Once he has scrubbed the chocolate off the seats, Macdonald heads to a local tea-room for lunch. Robin Robertson, the owner of a handicraft shop, drops in to ask him to put aside some tickets for The Other Boleyn Girl, bribing him with a Magnum from her freezer. Having moved to Harris from New York State nine years ago, she is one of the area’s growing immigrant population – or “incomers”, as they are called in slightly sinister, Royston Vasey fashion. “Some people think the incomers are changing everything but some things need to be changed,” she insists.

Some of Tarbert’s younger citizens have a similarly progressive outlook. Kirstie Young, 16, is looking forward to seeing Juno, admitting that its theme – teen pregnancy – is not entirely alien to the bored youth of Harris. She disagrees with the lack of screenings on Sundays: “It’s annoying – we have nothing to do then.” Is she not in church? “No!” She looks horrified.

With 15 minutes to go to the big evening screening, the auditorium is almost empty. Perhaps the villagers have gone elsewhere – the Harris football team are taking on their bitter rivals from Lewis. But arriving late is the done thing, according to Macdonald. “We are on island time now,” he reminds me. “And there’s no word in Gaelic that conveys the urgency of mañana.”

He even delays the screening for five minutes because Mrs Robertson and her girlfriends are still eating their premovie meal across the road. That Magnum has obviously done the trick – how many cinemas will wait for you to finish your banoffee pie?

The Screen Machine is on the Isles of Mull and Islay (Mon-Wed). For more information, visit screenmachine.co.uk; to book tickets, see thebooth.co.uk

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