A long time ago, in a galaxy far, far away, a little heralded film became one of the most successful movies ever. And, along with a whole industry devoted to merchandise and a devotion bordering on the religious, it helped create a new phenomenon the movie trail.

Hotels in Tunisia now carry plaques to proclaim their roles in the original Star Wars movie, as well as the most recent addition, The Phantom Menace.

Films can do wonders for tourism. Just ask the tea shops north of the border about the effect of Braveheart. Now, attractions up and down the country are hoping some of Harry Potter's magic will rub off on them.

Director Chris Columbus' decision to shoot The Philosopher's Stone entirely in this country must have had executives rubbing their hands with glee, waiting for the money to start rolling in when children persuade their parents to take them to see the 'real' Hogwarts school, the 'real' Platform nine-and-three-quarters and the 'real' Gringotts Bank.

The British Tourist Authority (BTA) is producing an updated version of its Movie Map, first published in 1996, to guide Potter fans to the film's locations.

Among the locations chosen by Columbus and his team were Alnwick Castle in Northumberland, Durham Cathedral, and Goathland Station, on the North York Moors Railway. The cathedral has asked not to be included on the BTA map. But Alnwick Castle and the North York Moors Railway have no such qualms, and are keen to reap the rewards for co-operating with a film that is already a record-breaker.

The omens are promising, going on the record of previous UK attractions. Broughton Castle saw its visitor numbers rise by almost 15 per cent after it appeared in the Oscar-winning Shakespeare in Love. Saltram House, near Plymouth in Devon, had even greater success, with a 39 per cent increase after it took a starring role in the Emma Thompson-scripted Sense and Sensibility. And Pride and Prejudice sent numbers at Lyme Park in Cheshire soaring by 178 per cent.

According to VisitScotland, 80 per cent of tourists going to the Wallace Monument outside Stirling said their visit was prompted by Mel Gibson's Braveheart, and in 1997 a report estimated that additional tourist income arising out of both Braveheart and Rob Roy amounted to £15m.

But Harry Potter looks certain to be the most successful of all.

A BTA spokeswoman says: "Harry Potter is big everywhere, and it is a very British film. All the cast are British, all the locations are British, and we're hoping it will draw visitors."

The new Movie Map is available at www.visitbritain.com/moviemap