Increased security measures at Oxford's largest hospital have led to a reduction in violence and thefts.

Improved CCTV and better use of security staff at the John Radcliffe Hospital has also meant a drop in the number of people wandering on to the site without a valid reason.

In 2005, staff and patients at the Headington-based hospital suffered an average of 105 acts of violence every month. The number has now dropped by almost one third, to 72 a month.

Ian Humphries, director of estates and facilities at the Oxford Radcliffe Hospitals NHS Trust, which oversees the JR, said security guards were being deployed in places where there was an increased need, such as in accident and emergency. He added: "A lot of people are violent as a result of their medical condition, but we do have a zero tolerance policy and an incident involving significant aggression is carefully considered and evaluated.

"There are times when it's clear a patient is behaving totally inappropriately and we adopt a very firm approach with them. We've taken people to court for that sort of behaviour."

Latest figures show that in 2006, four people were successfully prosecuted for common assault.

'Proactive' security measures have also led to a 42 per cent decrease in thefts at the JR. As well as better CCTV systems and staff awareness campaigns, police beat bobbies now visit the JR and the Churchill Hospital.

Mr Humphries said: "If there's something that looks suspicious we can follow people through the hospital and intercept them if necessary.

"People in hospital, both staff and patients, have lots of personal belongings like mobile phones, bags, cars and bicycles. We see opportunists come on to the site, and we've successfully attempted to eliminate them with awareness campaigns targeted at staff."

To reduce "opportunists" at the hospital, security guards have also started to get tough with people arriving with no valid reason. The number of people removed from the site has dropped from 41 a month in 2005 to 26 a month last year.

And "mystery shoppers" from Thames Valley Police Crime Reduction Team have visited various departments to see how far they can get without being approached. According to Mr Humphries they "didn't get far".

He added: "We often see people looking for somewhere warm and comfortable to stay - students in the wrong place at the wrong time or those a little down on their luck.

"We sometimes have people wandering on to the site who're worse for wear following a night on the town.

"It's a relatively small number, but something we're keen to keep on top of, to keep staff and patients safe."