THERE’S no mystery why tourism is booming in Oxford.

That’s the view of tourism bosses who say visitor numbers are soaring on the back of Lewis, Morse and Harry Potter.

Last night, television star Kevin Whately, who plays Detective Inspector Lewis in the ITV series of the same name, spoke of his delight at returning to film in the city.

He was at the University of Oxford Botanic Garden to film the show’s sixth series.

Mr Whately told the Oxford Mail: “I’m always excited to be back in Oxford and we are really enjoying filming this episode.”

Series director Brian Kelly said crews had been in Oxford since Monday, and hoped the series would be on our screens next spring.

He said: It’s great to be back and it is nice to be at the Botanic Garden. It’s the first time we have been here.”

Co-star Laurence Fox said: “Oxford is definitely a very nice place to be on a sunny day like today.”

Filming came as Visit Oxfordshire revealed it had seen a huge swell in the number of people calling into the Oxford Tourist Information Centre.

From April 2010 to March 2011, 531,000 people stopped at the centre – an increase of seven per cent, or about 35,000 people, on the previous year.

And the numbers are continuing to grow, with more than 230,000 visitors from April to July this year – a 10.5 per cent increase compared to the same period in 2010.

Visit Oxfordshire director Susi Golding said: “We run Harry Potter walking tours once a month and they are sold out for the rest of the year.

“We are quite lucky because we have Harry Potter, and Lewis and we still have people wanting to do Morse tours so it has had a big impact.”

She said tourism provided about 10 per cent of Oxfordshire’s employment – with 29,000 jobs across the county.

She added: “We have been surprised this year that numbers seem to have increased again because it was great last year.”

Approximately nine million people visit Oxford each year, and 27 million come to Oxfordshire.

Meanwhile, a study of the most popular sites by Visit England showed that the Ashmolean Museum, in Oxford, was the country’s most visited free attraction outside London, with more than a million visitors in 2010. Blenheim Palace, in Woodstock, also made it into the top 20 paid-for attractions, with 525,000 visitors.

Ms Golding said she had not noticed an effect on tourism from the recent riots.

Fans of Lewis said they were delighted to spot Mr Whately and Mr Fox, who plays Detective Sergeant James Hathaway, filming in the city.

Lorraine Gray, from Chinnor, said: “I think it is great that they keep coming back. Oxford is such a lovely city, so you can see why they choose it as a set.”

David Hack, who was visiting from Cumbria, said: “We were hoping to see them but we didn’t expect it.”

A NEW ENDEAVOUR * ITV has announced it will be filming a one-off show about Inspector Morse’s early career. Filmed in Oxford, Endeavour will be set in 1965 and stars Shaun Evans in the title role made famous by John Thaw. The original series ran from 1987 to 2000, when Morse died of a heart attack.