People working in intelligence are taught that it is easier to disguise their facial features than their mannerisms. Features can be changed, but mannerisms are so ingrained that it is hard to lose them. Everyone who is involved in assessing people looks at their hands.

Doctors examine their patients’ fingernails as intently as the face and eyes. The shape, colour and any other abnormalities of the nails betray both evidence of physical ill health and psychological tension and stress.

Doctors will check to see whether the nails have been bitten or picked, resulting in brachyonychia: nails shortened by being bitten to the quick. If the nail, especially the thumb, is also sucked, it will show markings from the teeth. These are signs of someone suffering from tension, and it is unlikely that any stress problems they have will be confined to biting nails. Gordon Brown is a son of the manse, driven by his conscience and Presbyterian ideals. He has an obsessive side to his nature and he wants to become Prime Minister so that he can achieve his objectives.

The Chancellor has altered since he married, but he is still under a great deal of strain — and he cannot hide those bitten fingernails.