A mother campaigning for medical marijuana to be available on the NHS is the director of a company which sells bottles of cannabis oil for more than £500.

Charlotte Caldwell is the sole director of Billy’s Bud Ltd, a cannabis oil distributor named after her son Billy Caldwell, the boy who was given first ever NHS prescription to help control his epilepsy.

A spokesman for Mrs Caldwell said profits from sales of the cannabis products, which include oils, capsules, powder, gummies, shots and honey sticks, were used to fund Billy’s 24-7 healthcare needs.

The oil she sells is CBD, a type of cannabis chemical which is legal in Britain because it does not make users high. It is not the same as the THC variety, which has mind-altering and psychoactive effects, and which is currently banned.

Yesterday Sajid Javid announced that the government was willing to review the law on the use of medical cannabis which could lead to patients in Britain being prescribed drugs from the prohibited plant.