The original football hard man Vinnie Jones has also changed his image by going on to front adverts for the British Heart Foundation, in which he performs CPR to the tune of Staying Alive.

Tough guys are really softies at heart, a study suggests.

Psychologists found that men with a more aggressive appearance – typically those with wider faces – were more likely to sacrifice themselves to help friends or colleagues.

The researchers, at the University of St Andrews, gave students money to play a game in which they could either enrich themselves or risk their cash to assist their group.

Dr Michael Stirrat said: “It was surprising... our participants with wider faces were more co-operative than the other men.”

Previous research had found that men with wide faces are judged to be aggressive and dishonest, while facial masculinity has also been commonly associated with a perceived lack of warmth and co-operation.

The university said the study, published this week, lends greater understanding to masculinity and male group behaviour and overturns previous theories that masculine looking men are “bad to the bone”.

Dr Stirrat, a researcher at the School of Psychology’s Perception Lab, said: “Dominant looking men - typically characterised by wide faces - are often portrayed as ‘bad to the bone’, but we wondered whether the relationship between facial width and personality was really so simple.

“We suspected that men who look aggressive and untrustworthy might actually be good guys in some contexts.”

One example is that of Terry Butcher, who famously played on for England in a World Cup qualifier in 1989, despite blood pouring from his head and covering his white strip after being injured.

Another is the late Colin 'Mad Mitch' Mitchell, the soldier who led the Argyll and Sutherland Highlanders in the British reoccupation of the Crater district of Aden in 1967.

'Mad Mitch', whose reoccupation of the Crater became known as “the Last Battle of the British Empire”, went on to manage a charitable trust involved in the removal of land mines.

The original football hard man Vinnie Jones has also changed his image by going on to front adverts for the British Heart Foundation, in which he performs CPR to the tune of Staying Alive.

The findings suggest that facial width may be related to performance and achievement because these men put more time and effort into groups of close friends and colleagues.

The results support recent research that showed that the facial width of male chief executives predicts their business performance and the facial width of male presidential candidates predicts their drive for achievement.

In the St Andrews study, half of the students given money by researchers were told that the outcomes of the game would be compared with St Andrews students, the other half that they would be compared with a rival university.

The prediction was that the wider faced men would respond to the rivalry in the second condition and sacrifice their money for their own group.

Dr Stirrat said: “It was surprising that our predictions were confirmed; when we mentioned the rival university, our participants with wider faces were more cooperative than the other men.

“When we didn’t mention the rivalry, they were much less cooperative.”

The researchers say that compared with women, men appear to be more sensitive to intergroup relationships, especially when they are being observed.

The results suggest that while more robust males may show more 'masculine' behaviour in anti-social ways, such as physical aggression, they are also more likely to make sacrifices to support the groups to which they belong.

Dr Stirrat said: “The same characteristics in men predict both anti-social and pro-social behaviour, depending on the context.” - Daily Mail

The study is published in the journal Psychological Science.