They are famous for staring down on Oxford as city life bustles by.

In the name of art, Roma Tearne blindfolded four of the stone emperor heads in Broad Street, Oxford, on Friday - although their 13 original cousins at the Sheldonian Theatre had to remain untouched as Oxford University said no to the stunt.

Mrs Tearne, an artist and novelist, who works at Oxford Brookes University, blindfolded four statues outside the Museum of the History of Science, for her artwork entitled Visions.

The display was part of the Oxford Inspires celebration of Oxfordshire's Millennium, and followed last week's Luminox fire installations, which lit up Broad Street for three nights.

Mrs Tearne said: "I wanted the public to look at these statues in a different way.

"For years, people have been walking past them and not really noticing them, but now they will look at them in a different way after seeing them blindfolded."

But the 13 neighbouring heads above the Sheldonian entrance were not used because the university authorities feared what it might lead to.

Mrs Tearne explained: "We approached the Sheldonian to blindfold the 13 statues outside but they said no because they thought it would encourage pranksters to put traffic cones or ladies' underwear on them.

"There hasn't been enough public art in Oxford recently and I think Oxford University has really missed an opportunity.

"I've done the same thing with statues in Rome that are 2,000 years old and no-one complained.

"The statues at the Sheldonian are replacements for earlier versions and only went up in 1972, so they are not particularly ancient."

Mrs Tearne's novel, Mosquito, is published by HarperCollins, and she appeared on Saturday at the Oxford Literary Festival.

No-one from the Sheldonian Theatre or Oxford University was available for comment over the weekend.

The 13 heads outside the Sheldonian were erected to mark its front boundary when it was built from 1662 to 1668.

When the Old Ashmolean - now the Museum of the History of Science - was built next door in 1679 to 1683, four matching heads were carved.

Some originally called them philosophers but eventually they were called emperors.

The heads we see today are the third set.

The originals lasted two centuries but by the mid 1800s began to crumble.

New heads were put up, but students vandalised them and they began to weather badly because of the harsh cleaning needed.

In the 1970s, sculptor Michael Black, along with two assistants, carved the new set.