Stealing college mascots, swallowing live goldfish, transforming domes into giant breasts - the student prank is alive and kicking, but, says Adrian Mourby, not everyone is laughing.

The 150ft-high Great Dome at Massachusetts Institute of Technology stands as a symbol of one of the world's top research institutions. But the dome is not sacred. Far from it. One morning in 1990, the sun rose not on the Great Dome but rather the Great Breast of Knowledge, or Mamma Maxima Scientiae. A large nipple and areola had been built in situ on the pinnacle overnight by students from the Burton One Outdoor Breast Society (Boobs) on what proved their fourth and final attempt.

Youthful high spirits have always been tolerated, even indulged, as part of undergraduate life. Most universities and their communities learned long ago to live with student pranks, many of which are in direct response to a long tradition that challenges each new generation to outdo rival students by getting one over university administrators in playful contests of cunning and guile.

The Great Dome at MIT has certainly provoked some imaginative responses in its time. The Star Wars generation turned it into R2D2 and more recently, the Dome's outer ring was inscribed in Elvish to celebrate the release of the film The Lord of the Rings.

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In Britain, the nocturnal Cambridge University Breaking and Entering Society (Cubes) has made it a point of honour to infiltrate the most allegedly secure of college buildings and leave behind a calling card - on one occasion a rubber duck. At University College London, Phineas, the lifesize effigy of a Scots Highlander, has frequently been stolen by students from King's College, London. King's students, meanwhile, have to keep a close eye on Reggie the Lion, the college's stone mascot, which is a frequent target for abduction by Imperial College students.

Stuart Jenkins was a veteran of the Imperial College Reggie the Lion Raiding Team of 1995. "We'd set our sights on Reggie partly because we'd discovered where it was kept and had a plan, and partly because the then president of King's student union had banned Imperial students from selling our rag mag on his campus."

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Jenkins, now sober-suited and working for Oxford University Press, was the brains behind a plan to forge a letter from the president of King's union that authorised a bogus firm of stonemasons to collect the mascot from its hiding place.

"Next morning, a nondescript minibus pulled up and a bunch of burly looking fellows got out, approached the security guard and waved their bit of paper. The guard took the bait, opened all the doors and even added: 'Don't worry if the alarm goes off, I'll sort it out once you're gone.'"

Unfortunately, the reprisal from King's displayed much less finesse - a raiding party smashed up Imperial's bar. "They did several thousand pounds worth of criminal damage to private property that was nothing to do with the those who kidnapped the lion," says Jenkins. "The game of mascotry was supposed to be fun. King's had a mascot and we had a plan. There was a gentlemen's agreement about conduct. Violence was not acceptable and the rules meant that to succeed you had to think."

Another prank that went too far was the live goldfish-swallowing incident perpetrated by Glasgow University freshers in 1999 during their annual "Iron Stomach" competition. Animal rights campaigner John Robins was enraged and asked the police and the university principal's office to investigate. "These students should be getting psychiatric treatment for what they've done," he claimed. "They obviously have no real regard for animal life. While students are entitled to be a bit mad during freshers' week, they are not entitled to be cruel."

Some communities, however, seem quite happy to embrace their students' excesses. In Glasgow recently, there was outrage when a traditional student prank - the traffic cone that has crowned the Duke of Wellington's statue for years - was removed so that city officials could take new promotional photos. Alex Mosson, lord provost of Glasgow, was dismayed by the duke's loss of headgear. "I was very disappointed. The statue of Wellington has become famous for the cone on its head. What began as a student prank has now become one of the city's best-known landmarks," he said.

In Massachusetts, the Hilltop Steakhouse, unwitting donor of a large plastic cow that in 1979 was discovered atop the Dome of MIT, now proudly displays its mascot outside the restaurant adorned with a mortar board on its head and an academic scroll in its mouth.

Perhaps there is a line that should be drawn between pranks that shock and amuse and those that shock and outrage. At MIT, which has a long tradition of "hacking", a balance has always been maintained between audacity and consideration for those who will have to clear up after the prank.

MIT historian T. F. Peterson has produced a book on the subject, Nightwork, that codifies the ethics of hacking. This 11-point statement stipulates that no clues to the hackers' identity should be left, no one's life should be endangered, no permanent damage should be done to college structures and, if possible, a detailed set of instructions should be left for those sent to dismantle the prank.

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Ingenious MIT students reached new heights of cunning in their attempts to disrupt Harvard University's annual football game against Yale University.

After being defeated by security precautions for a number of years, MIT regrouped in 1982 and carried out a triple whammy. Towards the end of the second half, as Harvard was trying desperately to even the score, a weather balloon 6ft across inflated and rose up from below the turf with the letters "MIT" clearly marked on it. Before anyone could remove the balloon, it exploded and covered players with talcum powder.

The second hack involved the Yale marching band, which turned out to be comprised of MIT students in disguise who then made straight for the centre of the pitch and lay down to spell out the letters "MIT". Meanwhile, an entirely independent hacking team was handing out 1,134 cards in the Harvard stands that should have read "Beat Yale!" when they were raised but in fact read "MIT".

Not every student prank has the intention of raising laughter, however. At Cambridge, John Casey, fellow of Gonville and Caius College, recalls an escapade that preferred to raise political consciousness. "Leftists went in for serious pranks. There was the banner that appeared one morning stretched between the two pinnacles high above the east end of King's Chapel denouncing the Vietnam war. It vanished two days later as mysteriously as it had appeared. Rumour had it that the domestic bursar of King's had promised a hunting and shooting undergraduate a case of claret if he would shoot the offending object down at first light."

Another prank with political ramifications was the theft of the Stone of Scone from Westminster Abbey in 1950 when four Scottish students, led by law undergraduate Ian Hamilton, reclaimed the monarchical stone for Scotland and kept it for 15 weeks before leaving it in Arbroath Abbey. No charges were ever brought, although to this day a question mark hangs over whether the original stone or a copy was returned.

Some stunts do bring the student prank into disrepute, however. St Andrews students certainly went too far in 1998 when they involved an unsuspecting member of the public, postman Alex Kirk, who was sent home from work in shock when he discovered a severed human hand in the pillar box he was clearing out. "I thought it was a dummy at first," Kirk said at the time.

"But then I saw the tendons quite clearly. All the flesh had been stripped away and it looked pretty horrible." The hand was a dissection specimen that carried a medical identification tag. University vice-principal Colin Vincent immediately apologised in writing to Mr Kirk.

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Faced with such behaviour, it is tempting to suspect that the heyday of the amusing prank is past, that student laughter has a crueller edge these days. But lest we grow sentimental for the Brideshead generation - all decent types just letting off steam - Evelyn Waugh himself recorded their barbarity in his novel, Decline and Fall, which chronicled what he called "the sound of the English county families baying for broken glass".

The book, written in 1928, opens with the dean and bursar of an Oxford college musing on which undergraduates will prove targets for the Bollinger Club that evening:

"'I think Partridge will be one; he possesses a painting by Matisse or some such name.'

'Austen has a grand piano.'

'Oh, they'll enjoy smashing that.'

It was a lovely evening. They broke up Mr Austen's grand piano and stamped Lord Rending's cigars into his carpet, and smashed china, and tore up Mr Partridge's sheets, and threw the Matisse into his lavatory."

High jinks and bad behaviour have always existed, and it is certainly nothing new for one to spill over into the other on occasion. Today, however, such excesses are far more likely to be ascribed to loutishness than high-spiritedness. Public and police are less tolerant.

"I think things have certainly changed here in London," says Peter Huggins, communications officer for University College Union. "My brother is at Oxford and they seem to be able to get away with blue murder up there while here we have to be careful. There used to be a lot of flour and egg fights between colleges up here, specially between UCL and King's, but recently some of our people broke into the LSE bar and flour-bombed them and they got summonsed."

But Huggins does hold out some hope for the future: "I have seen an email going round suggesting we get King's renamed 'Strand Polytechnic' in the autumn. That's encouraging."

Nightwork by T. F. Peterson is published by MIT Press, ?13.50.

Ten unforgettable pranks

? Canberra
Students fed up with inadequate parking at Australian National University hired a crane and lifted the vice-chancellor's car on top of his office

? Oxford
A don who had been working many hours decided to go into town only to find that the front door to his rooms had been bricked up for so long the mortar had set

? San Francisco
Engineering students suspended a Volkswagen from the Golden Gate Bridge claiming that they were trying to raise the awareness of engineering as an academic discipline

? York
Writer Victor Lewis Smith, while still a student, climbed scaffolding on the front of the Minster and called the faithful to prayer muezzin-style. He later complained about the lack of police violence when he was removed

? Cambridge
Engineering students succeeded in placing a mini van on top of the supposedly inaccessible Senate House roof using a system of pulleys to overcome a 5ft ravine

? Sydney
The steps to Australia's Central Bank were blocked by 150 garden gnomes that had been glued in place and had to be removed with industrial solvent before a board meeting could proceed

? Cambridge
A college principal opened his front door to find himself looking down the barrel of a very large piece of field artillery stolen by students

? Bradford
Students who dressed as vampires and staged a mock kidnap were shocked to find themselves besieged by police who believed they were dealing with real hostage takers

? Newcastle
The university abseiling team staged a dramatic entrance on to a floating night club moored under the Tyne bridge in a supposed protest at the high price of admission

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? And who could forget ... Manila
Onel De Guzman sent the infamous Love Bug computer virus round the world after AMA Computer College refused to accept his thesis showing how it could work.