A Mid Sussex hospital is taking part in a pioneering study into the potential painkilling effects of cannabis after surgery.

The Queen Victoria in East Grinstead is one of 35 hospitals in the UK signed up to run trials measuring the effects of cannabis plant extract against other pain relieving drugs.

Doctors carrying out the study for the Medical Research Council want to recruit 400 patients from across the UK to take part.

Each patient is randomly assigned one of four oral pain-relieving treatments containing either standardised cannabis extract, tetrahydrocannabinol (an active ingredient in cannabis), a standard pain relieving drug or a placebo.

The pain relief and side effects are then assessed over six hours and patients are questioned about their pain and feelings.

Anita Holdcroft of Imperial College London, who is leading the £500,000 trial, said anecdotal evidence suggesting cannabis could provide effective pain relief needed to be assessed scientifically.

She said: "We can only find definitive answers if people are willing to take part.

"As not every volunteer is likely to be eligible, I'd really like to appeal to anyone who is asked to consider taking part to take the time to question the researchers and look at the patient information and see if they feel able to contribute.

"The important thing to remember is no one will be left without access to pain relief during the trial, regardless of what treatment they are allocated."

Dr Holdcroft said if oral cannabis plant extract was found to be effective and without adverse side-effects, it could provide another pain relief option.

People taking part in the trial will need to be over 18 and cannot have had any exposure to cannabis or its constituents for six weeks prior to taking part.

Patients may withdraw from the trial at any point and this will not affect the medical care they receive.

Michelle Aylward, clinical nurse specialist for pain management at the hospital, said: "Clinical trials of this nature provide much needed research in an controlled, safe manner.

"This is an opportunity for the Queen Victoria to be actively involved in the sort of research that could have an impact on pain management in the future."