Last weekend I was in Cambridge (boo, hiss) for a party, and I don’t think I’ve ever felt so hot and harassed. By noon on Saturday I was sweating like a panda in a sauna. Trinity Street, home to two of the grandest colleges, had become a slow-moving river of people.

Add some placards and a few banners, and it would have made a decent protest march, but nobody was there to shout slogans.

They were just a tiny fraction of the many thousands of foreign tourists who visit Britain’s historic towns and cities every summer. In a few weeks Oxford will be just as busy. (It attracts visitors in roughly the same way that a magnet attracts iron filings.) Every summer the same scenes are repeated. Open-top buses chug along the High Street. Tour groups are whisked around the main sights by guides who wield their umbrellas like sergeant majors drilling a set of unwilling recruits.

Large crowds of people try to take photos of Oxford’s picturesque streets and buildings without anyone else accidentally drifting into the frame.

It’s probably fair to say that the main attitude of Oxford’s residents to these visitors is ambivalence. We recognise that a river of people also represents a powerful income stream. We are proud to live in a city that encourages them to stop and stare.

On the other hand, few things are as annoying as getting stuck on a narrow pavement behind 50 dawdling teenagers feigning an interest in gargoyles, especially when you know that all they really want to do is flirt with each other outside McDonald’s. The colleges are equally ambivalent. Some go out of their way to attract as many visitors as possible.

Christ Church, in particular, trades hard on its reputation as the architectural inspiration behind some of the Harry Potter sets, and on a busy day hundreds of curious fans can be seen swarming around its quadrangles like ants at a picnic. Magdalen is a bit quieter. Many visitors are interested in seeing the college where C. S. Lewis wrote the Narnia books, and seem a bit disappointed that we keep deer rather than lions or a captive Mr Tumnus. (It’s rumoured that one or two have hunted out Lewis’s old rooms and knocked on the door, asking a bewildered colleague of mine if they can have a quick look inside his wardrobe.) And, of course, those who have seen films like Shadowlands or Brideshead Revisited enjoy the experience of walking around a college that is like a living movie set. They examine everything. Every commemorative plaque is read, every flagstone paused over.

The only parts of the college nobody notices are the human beings who live and work there. We’re invisible — just another part of the background. And that’s just as it should be. When we’re teaching or researching, it’s easy to assume that we’re leading actors in a story. Sometimes it’s good to be reminded that for everyone else who comes here we are merely extras.

Robert Douglas-Fairhurst is a Tutorial Fellow at Magdalen College