You’d think it was the Grail itself we were seeking. Like the plot of Dan Brown’s ubiquitous novel, we seem to be caught in a game of cat and mouse involving cryptic clues, arcane rituals and pursuing cops — all for a glimpse of Tom Hanks.

“It starts with a B, that’s all I’m saying,” says the security guard in response to repeated questions from fans about which hotel is hosting the stars of The Da Vinci Code, currently filming behind a Road Closed sign in the tiny village of Roslin.

“B…B…Balmoral hotel?” frowns Carol Honeyman, one of a knot of seasoned autograph hunters trying to decode the clue that will lead to the Hollywood A-lister. “Naw, we tried that last night — nine hours waiting in the rain!” She shakes the rain off a cardboard placard that reads: Tom Hanks Please Stop and Sign! “If he doesn’t come out soon you can tell him I’m boycotting the film.”

It is hard to believe that the man reputed to be Hollywood’s nicest star is here in Roslin, although the tight security, chattering fans and glinting lenses of paparazzi cameras give a strong indication that all is not normal in the Midlothian countryside.

Armed with mobile-phone camera, paper and a pen, I have joined the enthusiastic group of self- proclaimed star stalkers that has taken up residence in Roslin.

Of course, I am something of an expert. Several years ago I met Roslin’s other world-famous celebrity, Dolly the sheep — not exactly talkative, but a veritable media slut in comparison with the invisible stars currently sequestered in the world-famous Rosslyn Chapel.

Less than 100 yards down a country lane, Hanks and the French star Audrey Tautou are filming the denouement of next year’s surefire box-office hit The Da Vinci Code.

Adapted from Dan Brown’s bestselling thriller, and directed by the Oscar-winner Ron Howard, the four-day location shoot is enveloped in the kind of neurotic security overkill you’d expect from a £53m movie about a religious conspiracy. The chapel is out of bounds, the access roads are blocked, and dozens of police and security guards are combing the surrounding woodland in search of cunning interlopers.

All of which is only increasing the determination of fans like us, grail aficionados and journalists gathered at the village crossroads.

Carol, 38, from Falkirk, has hundreds of autographs: Clint Eastwood, Samuel L Jackson, Michael Douglas, Dennis Hopper, Ralph Fiennes, Oliver Stone, Robbie Coltrane, Robert Carlyle. She’s already bagged Howard outside his hotel, and today she’s upping the ante, carrying two second world war helmets used in Saving Private Ryan, which she thinks would look much better with Hanks’s autograph on them.

“We’re trying to chat up the police so they’ll take something down and have him sign it for us,” confides her boyfriend, who is reluctant to give his name in case his colleagues find out his obsession. “But no luck so far. Apparently the paparazzi are in the forest doing manoeuvres — a bit sad really. Why don’t they just stand here like the rest of us?” I’m tempted to side with the snappers. With no joy from the official route — “a strictly closed set to all media for the entirety of production” — I’m all set to plunge into the undergrowth when a tabloid photographer races past. The cast has just spotted him perched up a tree with a telephoto lens and police are now patrolling the woods for chancers. I beat a hasty retreat.

The 15th-century chapel is the private property of the Earl of Rosslyn, who is renting it out for location fees expected to add £100,000 to the restoration fund. Prices are rather lower among the cabal of pensioners in overlooking bungalows who have rented out back rooms to TV crews for £75 a day. “It’s all going to charity,” says one retired schoolteacher, who agrees to let me have a quick peek across the apparently empty set for free on condition of anonymity.

The Da Vinci Code, for those who are not among the 25m readers to have bought the book, involves renowned American “symbologist” Robert Langdon (played by Hanks) flying around the world with glamorous French investigator Sophie Neveu (Tautou) in search of the Holy Grail. All the while they are pursued by sinister churchmen determined to cover up the possibility that Jesus was married to Mary Magdalene and spawned a royal bloodline.

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