ACTING as a guide to a group of over-sexed young Americans and some altogether more reserved Scandinavians had left Maureen Minton a little breathless.

Not even the task of holding the attention of teenagers in love could daunt her enthusiasm for imparting information on just about anything they could possibly want to know - at least about Oxford.

Maureen's expertise, it should be made clear at the offset, is in stained glass windows, the Pre-Raphaelites and Oxford University.

For she is one of 60 members of Oxford's Guild of Guides who step out from an office in Broad Street each day to show people around our city and its historic colleges.

Almost 3,000 walking tours embarked last year from the Oxford Tourist Information Centre, which is operated by Oxford City Centre.

Now, thanks to the likes of Lyra and Harry Potter the guided tour business is really gathering pace, albeit on a new footing.

This month, for the first time, visitors and locals are being invited to join official city council themed tours, which had previously been low-key events, largely organised on a private basis.

Inspector Morse tours have been operating on Saturdays for ten years. But Oxford is to get in step with other major heritage centres by laying on walks covering a diverse array of subjects.

It all started earlier this month with an Inspector Lewis tour, visiting sites featured in the Sunday night television dramas featuring Morse's former side-kick.

Oxford's other famous Lewis, the author of the Narnia Chronicles, is to be the focus of a tour later in the year, as is his friend J.R.R. Tolkien and Charles Wesley, the founder of the Methodist Movement.

But not all the themed tours are dedicated to people and television characters. There is a West End tour, which may disappoint foreign visitors expecting to be introduced to the city's glittering theatre land. But at least in addition to the Oxpens ice rink, magistrates' court and hostels, the city West End now boasts the thriving Oxford Castle heritage complex.

The new tours have certainly presented Maureen and her friends with new challenges. Still chuckling about her struggle to interest the American couples only with eyes for each other, she arrived from her lunchtime tour with Elizabeth Hudson-Evans.

The pair have both been guides for two years, and underwent nine months of training, during which time they also had to sit no fewer than four exams.

Elizabeth, already something of a whiz when it comes to Harry Potter, is now carefully preparing herself for the 'Pottering in Harry's Footsteps' tour.

She is taking it as seriously as any of the literary tours, applying the same principle that breadth of knowledge is everything. It is simply no good knowing that the Hogwarts Infirmary scene in the Philosopher's Stone was filmed at the Divinity School, if you do not know your Slytherin from your Snape. She has even had to undergo a test to ensure she can stand up to the rigorous questioning of young Potter fanatics.

New College (the medieval cloisters were featured in the ferret scene in the Goblet of Fire, apparently) and Christ Church (the staircase and dining hall appear during the sorting hat ceremony) are among the highlights of the tour.

But Ms Hudson-Evans revealed how she had to disappoint one sharp-eyed young visitor on one of the pilot Potter tours. "During the tour I pointed out the Radcliffe Camera to the group. And one of the children in all seriousness asked, 'is that named after Daniel Radcliffe?'."

The girl looked suitably crestfallen on finding it had nothing to do with the young actor who plays Harry in the films.

She is now busily making herself an expert on Philip Pullman's Dark Materials trilogy, along with all the locations in the film, The Golden Compass, in time for its release later in the year.

Not many of the hundreds of visitors taken around by Ms Hudson-Evans are aware that her delivery is undoubtedly polished as a result of her own experiences as an actress, before she quit to bring up her family. She has appeared on stage in the West End and toured Canada with the great Sir Ralph Richardson in the play Lloyd George Knew My Father.

But the new tour that she most enjoyed, earlier this month, focused on some of the great women associated with Oxford.

She is convinced that this along with other themed tours, 'Garden Tours', 'The Rivers and Rowing Regatta' and 'Architecture', will attract local people too.

"The thought struck me the other day, when a friend who lived in Oxfordshire rang to ask if she could go on a stained glass tour birthday present."

Ms Minton is able to reel off a long list of films featured in the new Oxford Immortalised tour. But she points out that everything depends on the goodwill of the real stars of all the tours - the Oxford colleges.

"The colleges have every right to close their doors. But they tend to be very generous," she said.

But the doyen of the Inspector Morse guides, Bill Leonard, will tell you things are getting increasingly tight, with the likes of University not allowing guides in, and Trinity, Balliol, Brasenose, Magdalen and Christ Church having introduced charges.

"Before I started, 13 years ago, all the colleges were open all of the time. These days we make do, but it is getting more and more difficult. If it gets any tougher, I can see some guides giving up the job. They will just feel too frustrated about having to walk past places they know they can't go into, and not being able to give consumers the tour that they would like to give them."

Remarkably, the Lewis programmes featured more scenes of Oxford's golden heart than Inspector Morse had. But it seems the series went out a month late, meaning that Mr Leonard's Lewis tours began before all the programmes had been shown.

Mr Leonard is already planning a supplement on Lewis to his Oxford of Inspector Morse book - so Inspector Lewis tours look to be here to stay.

It certainly looks like themed tours will bring in valuable revenue for the city council, with adult tickets priced at £7 (£8 to Potter in Harry's Footsteps), adding to the impressive total of 1,500 pre-booked tours last year.

With Oxford being full of thousands of book-lovers this week, here to attend the Oxford Literary Festival, special literary walking tours will take place today and on Sunday, visiting city sites associated with great writers.

The 30,000 visitors expected at the festival will, in fact, be spoilt for choice, with official festival tours, such as 'Keats's Eyelashes' and 'Political Oxford', taking place through the week.

In the longer term, the city council themed walks will face stiffer competition, too, from a host of independent guides, with only a few dedicated entirely to one minority subject.

Usually, it is a question of group organisers asking for special interests to be included in a standard tour. Recently, however, even the National Lottery has become involved.

Part of a £45,900 Lottery grant has helped create a walking tour exploring the history of black people living and working in the city. The black Oxford weekend tours will start in June, following pilot walks last October.

In the summer months, evening tours are proving increasingly popular, with conference delegates and others tied-up in the day walking around the floodlit university buildings or joining ghost tours recounting the haunted and ghoulish past of the city.

One walk guide will even find you a place to propose to your partner at midnight in a romantic, unforgettable place, although it comes with no guarantee as to the result.