A 13-year-old epileptic boy whose case led to the legalisation of medical cannabis in Britain has been given his first legal dose the country.

Billy Caldwell and his mother, Charlotte, from Castlederg, Co Tyrone, returned from three months in 'exile' in Canada yesterday.

They were forced to leave Britain in November because they were unable to find a doctor willing to prescribe medical cannabis - despite it now being legal.

Billy Caldwell and his mother, Charlotte, from Castlederg, Co Tyrone, returned from three months in 'exile' in Canada yesterday.

The pair landed at Heathrow Airport and pick up the cannabis from a pharmacy in Surrey after being prescribed it by a doctor who was told by the Department of Health it was okay to write a prescription for the medicine.

Since taking the medicine, Billy who suffers from severe epilepsy, has been almost fit-free.

An overjoyed Mrs Caldwell told The Times: 'I scoured the UK and Ireland for doctors who would dot this. I have lost count of how many emails I sent and phone calls I made. I'd be there in Canada [sending messages at at three or four in the morning because of the time difference.

'I'm a wee bit emotional, it feels like I am getting out of jail.'

Mrs Caldwell, who paid for the prescription, said Billy would probably be the first person since NHS reforms to be prescribed the medicine on the NHS.

She added the Billy would die without taking the medicine.

Billy was given one NHS prescription for cannabis in 2017 - but the Home Office then banned his GP from giving him any more by the Home Office.

Last summer, when the family tried to bring in a fresh supply of medicinal cannabis from Canada where it is legal - it was seized by customs.

Since taking the medicine, Billy who suffers from severe epilepsy, has been almost fit-free

Billy was then thrust into the spotlight by his mother who made an appeal in the media for the law to be changed to allow medical cannabis to be legally prescribed - and said Billy could die without it.

Four days later she was pictured cradling him on the way to London’s Chelsea and Westminster Hospital.

A tearful Charlotte, 50, spoke outside the hospital about her ‘beautiful, sweet, innocent boy’ who was suffering ‘life-threatening’ seizures and didn’t deserve this ‘callous treatment’.

Within hours, the Home Office released some of the confiscated medicine, which contains two cannabis-derived substances, the legal cannabidiol (CBD) and banned tetrahydrocannabinol (THC), the psychoactive compound associated with the ‘high’ given by the drug.

They gave doctors a 20-day licence to administer one of the seven bottles of the drug Charlotte had brought from Canada.

Then, clearly feeling forced to act, Home Secretary Sajid Javid told the House of Commons it was ‘time to review the scheduling of cannabis’ for medicinal use.

Mr Javid's review led to a change in the law.

Patients' groups say the reform has had little effect and could be negative.

The pair were forced to leave Britain in November because they were unable to find a doctor willing to prescribe medical cannabis - despite it now being legal

Mrs Caldwell released a video from her son's room in Chelsea and Westminster Hospital where he received his cannabis oil treatment

The remarks from the patients' group triggered new guidance from professional bodies which discouraged doctors from prescribing cannabis.

One body, the British Paediatric Neurology Association, received letters from more than 30 parents - who had accused it of 'ignoring the law change' and causing 'barriers and threats to those seeking treatment'.

Charlotte said that for the first time 'connections had been made' between the medicinal cannabis experts in Canada and doctors and the UK.

She said 'it was a huge step forward for us in the UK - and not only Billy'.