By Jamie Doward and Lily Gordon Brown, The Guardian

Up to 20,000 patients in the UK are to be given medical cannabis over a two-year period in an initiative that aims to create the largest body of evidence on the drug in Europe.

The move, to be unveiled on Thursday, is backed by one of the UK’s leading medical bodies and it is hoped it will persuade the NHS to prescribe the drug for a range of conditions.

Although medical cannabis was legalised in the UK a year ago, it remains unobtainable for many patients, according to campaigners.

“Medical cannabis is still out of reach for far too many,” said Professor David Nutt from the independent scientific body Drug Science, the organisation behind the launch of Project Twenty21, which will see 20,000 patients supplied with subsidised cannabis products by the end of 2021.

“Patients are left untreated, in significant debt from the cost of private prescriptions, or criminalised as they are forced to turn to the black market. They don’t deserve any of this, and the situation with prescribing desperately needs to change.”

The project – which will be launched at, and is backed by, the Royal College of Psychiatrists (RCP) – aims to create the largest body of evidence on medical cannabis in Europe, to convince policymakers that the drug should be made as widely available, and affordable, as other approved prescription medications.