When should you retire - assuming you are relatively healthy. The Duke of Edinburgh chose 95 as his limit, though he has been scaling down his duties since his 90th birthday.

Dr Frankland is 105 years old and is still practicing as an allergy specialist. In fact when we were with him somebody rang to seek his advice on a case. So how does he stay so fit?

Dr Frankland gave the Today programme peek into his morning routine.