The Tudor king’s anger, forgetfulness, impulsiveness, headaches and insomnia were most probably caused by a head injury which left him unconscious for two hours.

Neuroscientists in the US researching Henry VIII’s many ailments have reached the same conclusion as many historians – that a traumatic brain injury sustained during a jousting tournament in 1536 altered his behaviour for the worse in the decade before his death in 1547.

In his prime Henry was described as an attractive, artistic and even-tempered king who made wise military and political decisions. He was also a highly skilled jouster. To him it was more than just a sport – it was a vital part of his kingship, modelled on the chivalrous masculinity of the medieval knight in shining armour. It was also very dangerous. In 1524, a lance penetrated the visor of his helmet during a tournament and dazed him.

Henry suffered another major head injury a year later when he was knocked out falling head-first into a brook while trying to vault across with a pole.

However, it was thought to be the jousting accident in January 1536 which triggered his behavioural change. Henry was unseated from his horse, which then fell on him and caused him to lose consciousness for two hours. He also suffered a serious leg wound and was so badly injured it was thought he may die.

When news of the accident reached Henry’s second wife, Anne Boleyn, she went into shock and miscarried a male child. A few months later, when Henry had recovered from his injuries, he had Anne executed on Tower Green.

The rest of his reign became known for his dissolution of England’s monasteries, his multiple marriages and the execution of his opponents, former advisers and another of his queens, often without trial, as well as his personal extravagance and numerous costly wars. He became severely obese, partly as a result of his festering leg wound, and is frequently characterised in his later life as a harsh and insecure king prone to rages, mood swings, impulsive decisions and forgetfulness.

Professor Arash Salardini, behavioural neurologist, co-director of the Yale Memory Clinic and senior author of the study said: “It is intriguing to think that modern European history may have changed forever because of a blow to the head. Historians agree his behaviour changed after 1536”.

The study’s findings are to be published in the June issue of the Journal of Clinical Neuroscience.