Scarlets flanker John Barclay has blown a huge hole in rugby’s concussion testing system by revealing he could have played when he knew he still had symptoms.

The Scotland captain has given a detailed account of how he passed all the medical tests following a concussion injury, but judged he was still not fit.

Barclay – who will make his full comeback when he skippers the Scots against Samoa at Murrayfield this weekend – was knocked unconscious playing for his region against Edinburgh on September 23.

In an account that will cast more doubt on the sport’s ability to provide a proper duty of care, Barclay has revealed he passed all the tests currently required within the regulations and could have returned after a couple of weeks, but knew he was still suffering from dizzy spells.

The 30-year-old said: “I passed the cognitive function test, and technically I could have said I felt fine. That to me is where the system is so flawed.

“If I had said I felt fine I could have played because I had passed all the tests but I still did not feel right, so right there is obviously where there is room for improvement in the assessment of players.”

Barclay’s concern is that some players – less experienced and less secure of their places within a squad – may be inclined not to provide medical staff with the full picture.

“I have played at bit of rugby, I have two kids and my wife is pregnant. I am not going to risk long term ill health or do something stupid just so I was fit to play in a rugby match, whether it was playing for Scarlets or Scotland.

“Everybody knows not to come back if your symptoms persist, it’s just whether you choose not to. Where you are in your career can affect that decision, but I think I am smart enough not to do that.

“That is just my approach but I know some of the other guys may not have done the same.

“It’s still frustrating because there’s no golden rule for it. It takes as long as it takes. I had some symptoms and had to just wait and bide my time for things to go away.

“I’ve had head knocks before but I wouldn’t say I’m prone to them. I’ve had my fair share as a professional rugby player but it was one of those ones that just dragged on a bit.

“In one respect it was one of those things you’ll look back and probably think it was a good time to get a break, and my body will probably better for it. But the symptoms I had and the way concussions are it was hard to relax for all those weeks.

“I was irritable, had migraines. It was not even a case of sitting back, maybe doing weights or other stuff. It was a case of doing very little for six weeks.”

Barclay revealed that after the collision with Scotland squad colleague Magnus Bradbury, he suffered migraines, dizzy spells and felt sensitive to light.

“I went for brain scans and stuff which sounds quite extreme and scary, but they found that everything’s okay, which obviously puts your mind at rest,” he continued.

“The stuff clubs do is great as a preliminary, but this was way more detailed and takes hours to do. The professor there admits what he’s doing isn’t perfect. He’s trying to find stuff that’s going to give them a better idea of how to treat these things.

“So he just said your cognitive function’s good, your brain is actually okay, so you just need to start trying to get back into things.”

“But he couldn’t explain the light-headedness and irritability – that’s the worrying thing, he’s a professor and he still doesn’t really know.”

Barclay featured for 60 minutes during the Scarlets’ win over Benetton and will now captain his country through their autumn series.