Billy Caldwell has celebrated his 21st birthday at his home in Castlederg, County Tyrone. In 2005, doctors told his mother Charlotte Caldwell that Billy, who has a severe form of epilepsy and is autistic, was not expected to live past his first birthday.

Charlotte Caldwell said that at times Billy experienced hundreds of seizures each day, was tube fed, and could not stand. After a combination of medications stopped working in 2010, she took him to a specialist in Chicago who adjusted his treatment and diet, which controlled the seizures for a period.

In June 2016, the seizures returned when Billy was almost 11. The family consulted the specialist again, now in Los Angeles, who referred Billy to a medical cannabis expert. Treatment with cannabidiol, or CBD, a non-intoxicating chemical from the cannabis plant, eased his symptoms.

The family returned to Northern Ireland in 2017 and a GP prescribed further doses. In May 2018, the NHS told the GP to stop prescribing because UK law required cannabis-based treatments to be based on clinical trials. The family then travelled to Toronto, Canada, where a paediatric neurologist prescribed CBD.

When the family flew back to the UK, customs officials at Heathrow airport confiscated the medicine. Billy had a seizure three days later and was taken to Chelsea children's hospital in London. Hospital staff could not give him the confiscated medicine because it was held by the Home Office.

The UK government subsequently granted the family a licence for cannabis oil and later relaxed laws governing access to cannabis-derived medicine after accepting evidence of therapeutic benefit for some conditions. Billy returned to Northern Ireland and received treatment on the NHS.

Billy's seizures stopped, except for a week in 2023 during a temporary supply problem. Charlotte Caldwell said he can now walk, has improved balance, can go up and down steps, and enjoys trips to the beach even in winter.

Charlotte Caldwell said NHS prescriptions for cannabis-based medicine remain severely restricted, forcing many patients to use a private system that is expensive and inconsistent. She has founded an advocacy group, Transparent Responsible Adult-Use Controlled Data (TRACD), to lobby for change.