A potential student on a trail dive declared yes to taking medication to prevent epilepsy. I sent him to a doctor who, knowing nothing about diving, wouldn't sign his medical. The student has not had a seizure for ten year and takes Tegretol Retard, 200mg two a day. Is it worth him seeking a further opinion?

Epilepsy is generally considered an absolute contraindication to diving. While underwater a diver may be exposed to possible triggering stimuli for seizures, including glare, flickering lights, sensory deprivation, hypervantilation and increased oxygen partial pressure.
Having a convulsion underwater often involves breath holding during the fit, making pulmonary barotrauma a high risk, as well as drowning.
These are the existing recommendations about the subject:
BSAC Medical Committee: "an epileptic can be permitted to dive after five years free from fits and off medication. Where the fits were exclusively nocturnal, this can be reduced to three years" Underwater and Hyperbaric Medical Society - Diving Committee: " individuals with epilepsy, who have been seizure-free for five years and take no medication, who chose to dive should be advised to avoid hyperventilation and cautioned that elevated pressures of oxygen may precipitate seizures.
Individuals with controlled epilepsy (taking medication, seizure free for two years) are advised not to dive.
Although the potential student you mention has been seizure-free for the last ten years, this has occurred under constant medication; therefore, based on the above, this individual should be advised not to dive.
However, should the potential student wish further and specialized advice, I am copying this message to the Area Director of DAN Europe English Language Area (Dr. R Cali-Corleo) and to the Medical Director of DAN Europe UK ( Dr. John Ross ) who may help in identifying a specialist in the area where the potential student lives.