THE River Cherwell beneath Magdalen Bridge in Oxford is only 20-30cm (8-12in) deep in places - and anyone who jumps into it risks breaking a leg.

With less than a fortnight before the annual May Morning celebrations, paramedics have issued a stark warning to those thinking of jumping from the ancient structure - do it and you are guaranteed at least a broken leg.

We went to see how deep the water was and, in parts, it barely measured the length of a ruler.

Police, council officials and paramedics met to discuss how to handle the early morning festivities and agreed to close the road between 3am and 9am on May Day.

On Tuesday, May 1, the bridge will be guarded at each side by 30 police officers, private security guards and fencing in a bid to stop students leaping into the shallow water - and possibly to a lifetime in a wheelchair.

Paramedic Adrian Fellows, of South Central Ambulance Service, said: "If you jumped you would be looking at a minimum of a broken leg.

"There's the potential for fractures and impact is going to damage the back, neck and lower limbs.

"There is also debris, broken bottles, discarded needles - and the risk of infection from open wounds.

"In 2005, ten people were taken to hospital and it took five ambulances to transfer them. Someone on the bridge said you could hear the snapping of bones.

"Fifteen seconds of fame could mean a lifetime in a wheelchair."

Each year, thousands of people turn up to hear Magdalen College choir sing the Hymnus Eucharisticus at the top of the college tower at sunrise.

The 25ft-high bridge was closed last year for the first time since 2001.

Only five people defied the ban and jumped - after the bridge reopened to traffic.

Yesterday, Mark Blandford-Baker, the college's home bursar, said: "At the moment the river level is comparable to how it was in the middle of August last year - there isn't a depth that is safe."

The emergency services added that the bridge would be closed for the foreseeable future if people defied their warnings.

Oxford police commander Supt Jim Trotman said: "All the time I'm around I will lobby for the safest means possible - and if that means closure, then closure it is."