Agricultural entrepreneurs William and Neil Ewart have been given planning permission to build the pioneering facility in Langholm, where the drug will be grown for use in medicines.

Medical cannabis products containing THC, the drug’s psychoactive compound, were illegal in the UK until the law was changed in November 201 to recognise evidence that medicinal cannabis benefits some patients.

Specialist doctors can now prescribe medications based on cannabis, which are most commonly used to treat epilepsy or chronic pain.

Neil Ewart said: “This is an excellent step in the correct direction but there are so many other steps to be taken.”

The 1.5-hectare greenhouse is expected to produce 200 litres of cannabis oil a year, which will be made on site from the raw plant material.

The oil will be extracted from the plant and bottled before being sold to pharmaceutical companies who will turn it into a medicine. About 50 people will be recruited locally for jobs.