Neil Greenberg is a world leading expert, and practitioner, in military mental health.

He signed up to the Royal Navy while still in medical school, then travelled the world on ships and submarines, not just attending to crew health but getting stuck into everything else required of an officer to keep a vessel operating successfully.

But it could have been very different, had he not heard a radio interview by chance.

Professor Greenberg tells Kate Gerbeau how the medic of a luxury liner inspired him to mix healthcare with adventure, all with the aim of making a difference.