A clash of heads with Stirling Mortlock at the start of Wales’s 21-18 win over Australia saw the Wallabies captain leave the field.

But Roberts played on for some 15 minutes with the fracture, an injury which Welsh team doctor, professor John Williams, admitted he had not seen before.

Williams said 22-year-old Roberts – a medical student himself – would be out of action until the middle of January, three weeks before the Welsh begin their defence of the championship.  

“I’ve never seen anything like this and I was talking to some of my colleagues and they have never seen anything like this,” said Williams.

“It was a collision of heads at a certain angle with a certain momentum causing a crack.

“Second week of January he could be back in contact which is three weeks before the Six Nations. We will just watch over the next two or three weeks while this heals.”

Williams added: “He was admitted last night with a fracture to his skull. He is comfortable, pain-free. He will be out of training for six weeks to give it a chance to heal and then back in the New Year.

“It is a fracture extending back from above the nose along the roof of the eye towards the central structures in the base of the skull. 

“It is a clean fracture which should heal very easily. It’s an undisplaced fracture so it means that it is a crack which hasn’t moved so it hasn’t caused any internal damage to the brain.

“After the contact Stirling Mortlock looked like he had come off worse. Jamie was conscious throughout and there were no signs of anything, no suggestion of a fracture or any problem with his nose or eyes. The contact was with his forehead.

“And then the headache gradually came on as he was playing about five minutes after and we pulled him off as the headache got worse.

"He is a pretty tough guy. He texted the team (from the hospital) and the team thanked him for taking Stirling Mortlock out of the game!”