Former England hooker Steve Thompson has announced he has been diagnosed with early onset dementia and declared he cannot remember being part of the team's 2003 Rugby World Cup triumph.

The 42-year-old, who spent most of his club career with Northampton, is one of eight players reportedly planning to take legal action against World Rugby, the Rugby Football Union and the Welsh Rugby Union. Former Wales back-rower Alix Popham is among those players.

According to the Guardian, the players, who are all also reported to have suspected chronic traumatic encephalopathy (CTE), will claim those rugby authorities failed to provide adequate protection against cases of concussion.

CTE is a progressive brain condition that has affected boxers and American football players previously, with medical experts believing it is caused by blows to the head and incidents of concussion.

Thompson played throughout England's World Cup final against Australia, which was settled by Jonny Wilkinson's last-gasp drop goal in extra time, but now he says the memories have gone.

"I can't remember it. I've got no memorabilia. I've got no feelings about it," he told the Guardian. "You see us lifting the World Cup and I can see me there jumping around. But I can’t remember it."

Thompson has no doubt the intense demands of rugby, and particularly the nature of training sessions in the early days of the professional era, have brought him to where he is today.

"It's the rugby that's put me through this," Thompson said.

Thompson suspects the eight players who have enlisted legal representation are far from alone in suffering such effects from playing rugby union.

The sport became professional in the wake of the 1995 World Cup, and Thompson suspects the early years of the paid era, as the sport transitioned to its new ways with full-time training, is when players were at their most vulnerable.

"I can see the numbers being high, especially for the first players to come through, what, ’96‑97 up to the mid-2000s, really," Thompson said.

"The 2011 World Cup camp was completely different to the 2003 World Cup camp. In 2011 it was a lot more technical, whereas in 2003 you just had to beast yourself."

He said at times when he was with England, "they literally just beasted you until you fell apart", describing the demands on players as "brutal".

Thompson believes there was sufficient expertise in the ranks of non-playing staff to know something was not right.

He said: "You think how many specialists were out there watching that and not saying anything.

"They knew what was happening. And nothing was done about it. People were getting knocked on the head and it was not being recorded. I'm knocked out in training and it was always: 'It's just a knock on the head, he’ll be fine.'"

Stats Perform News has asked the WRU and World Rugby for a response.

The RFU said in a statement: "The RFU has had no legal approach on this matter. The Union takes player safety very seriously and implements injury prevention and injury treatment strategies based on the latest research and evidence.

"The Union has played an instrumental role in establishing injury surveillance, concussion education and assessment, collaborating on research as well as supporting law changes and law application to ensure proactive management of player welfare."