Wales are coming under increased scrutiny over the circumstances that allowed Tomas Francis to return to the field at Twickenham despite suffering what appeared to be a serious head injury.
In an open letter to the Welsh Rugby Union, World Rugby and Six Nations bosses, lobby group Progressive Rugby, which is made up of a number of former and current players, as well as medical experts, described what unfolded as "a clear and flagrant breach of HIA protocol".
TV footage captured Francis staggering near his own try line in the 20th minute after a clash of heads with team-mate Owen Watkin, appearing to have to use the pads of the posts to hold himself up.
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He initially remained on the pitch after being checked by a medic before being removed to undergo a HIA, which he duly passed before returning to the pitch around 10 minutes later.
But, under World Rugby laws, any player who shows visible signs of balance disturbance/ataxia after a head blow should be removed immediately and permanently from a match without a HIA.
Francis continued to play before being replaced by Leon Brown in the 56th minute.
Watkin was left bloodied by the incident but underwent a HIA and passed.
In the strongly worded open letter, which has been made public, Progressive Rugby say: "Francis attempts to stand and falls back and struggled to get to his feet. He is seen holding his head. He is then seen using the post for support. He displays clear signs of ataxia and of being dazed. He is seen by a physio/medic – it is not clear which because they all insist on tabards wearing Medic.
"Francis displayed clear symptoms/indications under of the World Rugby Head Injury Assessment protocol that necessitate the immediate and permanent removal from play. No HIA was needed.
"While, after a delay, Francis was removed from the field he was, incorrectly, allowed to undergo an HIA assessment and returned to the field, playing until the 56th minute, at which time he was permanently replaced by Leon Brown.
"Progressive Rugby is concerned that the events demonstrate that individuals who have incurred brain injury have continued to be permitted to play which will place them at likelihood of risk. We consider the above incident demonstrates a clear and flagrant breach of HIA protocol that potentially puts both the short-term and long-term health of an elite athlete at risk.
"In addition, we still await the outcome of investigations into the failure to remove Jack Nowell from the field during the game against Italy (13th Feb) and behaviour of the England medical team at the culmination of the Italy v England U20 game (11th Feb).
"It is our major concern that the public has observed that in Rugby Union individuals have incurred brain injury and been permitted to continue to play.
"Until satisfactory explanations are provided, we remain unable to accept World Rugby’s assertion that player welfare is the game’s number one priority."
The WRU has been asked for comment.
Following the match, WalesOnline asked Wayne Pivac to explain what had happened, with the coach saying: “They go through some testing behind the scenes. They both passed the testing so they’re allowed to play on. They’ll go through more testing after and if they clear that, they’ll be allowed to train.”
The letter has been written by Professors John Fairclough and Bill Ribbans on behalf of the entire Progressive Rugby organisation.
The lobby group was formed last year to ask for more to be done to protect the well-being of players from excessive workloads, brain trauma and the consequences that come from repeated concussive and sub-concussive injuries.
Progressive Rugby is led by former Canadian international Jamie Cudmore, ex-England back-rower James Haskell, former Wales flanker Alix Popham and senior medical figures from the game. The likes of Wales player Josh Navidi and former star Jonathan Davies are also signed up members.
They have proposed a number of suggestions to World Rugby - including a limit on contact and workload in training, only allowing substitutions for injuries and regular check-ups for players.
The introduction of the lobby group comes after nine former rugby players, including Popham and Thompson, launched legal action in December against World Rugby, the RFU and the WRU for alleged negligence.
Each of the nine players involved are under the age of 45 and have been been diagnosed with - or assessed to be on the trajectory towards diagnosis of - traumatic brain injury, early onset dementia and probable CTE.
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