It is a hand gesture which has been seen in ancient mosaics and paintings for hundreds of years but now the reasoning behind the Pope's distinctive benediction sign may been solved.

First used by Pope Peter, it is thought the unique gesture, in which the thumb is tucked into the palm and the index and middle finger are raised together, may have been due to nerve damage.

New research from Dr Bennett Futterman, an anatomy professor at NYIT College of Osteopathic Medicine, reveals the Pope's gesture was started because his ulnar nerve had been damaged.

Pope Pius XI makes the distinctive hand gesture, believed to have been first used by Pope Peter

Pope Paul Vl (left) and Pope Pius XI (right) give the benediction sign, thought to have started due to Pope Peter suffering nerve damage to his hands

Pope Peter was left being unable to open his whole hand properly, making it difficult to make the 'Vulcan'-style salute, long used as a blessing by Jewish high priests.

'A fist has always been a symbol of war - it's never a positive position. No holy man would ever bless the faithful, a crowd, or followers, by making a fist,' Dr Futterman said.

'Peter, the first pope, had an ulnar nerve injury and everyone copied him. Imitation is a great form of flattery. Out of respect for St Peter, the other popes followed with that same pattern,' he suggests.

Pope John Paul II pays a visit to England and conducts a service at Westminster Cathedral in May 1982

Pope Pius XII gestures to the large congregation as he is carried through St Peter's Cathdral

Pope Francis has even been seen making the 'I love you' hand gesture whilst worshipping in the Philippines

Writing in Clinical Anatomy, the former surgeon studied numerous carvings and paintings of the benediction hand gesture, closely examining the possible reasoning for Peter's hand.

'Later, Peter was trying to do that - he would have blessed people the way he knew. But if you have an ulnar nerve injury, you can't spread your fingers and you can't extend your pinky and ring finger,' he said.

The median nerve stretches from the shoulder to the hand. If it was damaged, Pope Peter would have struggled to make the open palm gesture.