Like most visitors to London, Klaus Matzka and his teenage son Loris took several photographs of some of the city's sights, including the famous red double-decker buses. More unusually perhaps, they also took pictures of the Vauxhall bus station, which Matzka regards as "modern sculpture".

But the tourists have said they had to return home to Vienna without their holiday pictures after two policemen forced them to delete the photographs from their cameras in the name of preventing terrorism.

Matkza, a 69-year-old retired television cameraman with a taste for modern architecture, was told that photographing anything to do with transport was "strictly forbidden". The policemen also recorded the pair's details, including passport numbers and hotel addresses.

In a letter in today's Guardian, Matzka wrote: "I understand the need for some sensitivity in an era of terrorism, but isn't it naive to think terrorism can be prevented by terrorising tourists?"