Smoking is one of the biggest killers in Britain today: each year it leads to just under 80,000 deaths and about half a million hospital admissions. The cost to the NHS is estimated to be at least £2 billion.

The good news is that each year tens of thousands of people are giving up smoking with the help of e-cigarettes — devices that mimic the act of smoking but without the toxic tobacco smoke. They are about 95 per cent less harmful than conventional cigarettes.