Some years ago, as anti-capitalists marched on London, a statue of Winston Churchill was defaced. We all knew the correct reaction to such wanton vandalism was disgust, or at the very least a loud and disapproving tut, but somehow the addition of a turf mohican was impossible to resist.

It's the same with traffic cones. Students who steal them are bad, but if they make the effort and place them on the bronzed head of a historical figure, it's suddenly a photo opportunity.

So to York. A few weeks ago, prints of famous works of art by the
likes of Manet and Stubbs popped up in 49 locations, turning the
city centre into an al fresco art gallery overnight, with visitors invited to take an artistic Grand Tour of Europe.

Even before the last print had been hung, many were wondering whether it was worth starting a sweepstake on how many hours, possibly minutes, would have passed when the first one found a new home in a bedsit. As it turned out, not that long.

In the month or so since the exhibition began, three of the collection have been stolen and although all were later recovered, professional restorers have had to be brought in on an almost daily basis to remove grafitti.

So far, so contemptible. However, while those blessed with sturdy moral fibre made "I told you so" faces, as details of the vandalism became known, weaker souls could only unconvincingly nod their heads
in agreement.

Early incidents were admittedly predictable. However, while it may not have taken an art historian to spot that the joint which Christ appeared to be smoking in Caravaggio's Supper at Emmaus or the telephone in the hand of Madame Moitessier in Jean-Auguste-Dominique Ingres's portrait were later additions, it was hard not to admire the originality of whoever placed a paper bag over the head of the Grotesque Woman.

Okay, it's wrong, very wrong, but even Michael Woodward, director of business development at the York Museums Trust, has given credit where it was due. "We appreciate the imagination that some people have put in," he said, no doubt through gritted teeth.

"But we do urge them to stop and let everyone enjoy the paintings in their original condition."

Being lucky enough to live in York and not being a regular visitor to art galleries, I have unexpectedly seen more masterpieces in the last four weeks than I probably have in the last four years.

Whoever dreamt up the idea of the Grand Tour deserves enormous credit.

The vandals may have succeeded in amusing the weak-willed – me among them – but paper bags and nipple rings aside, their efforts haven't yet managed to overshadow one of the most impressive attempts to bring art to the people.