Lawyers are expected to have their work cut out for them in a concussion lawsuit against British rugby bodies.

Seventy ex-players are thought to be involved, including about five ex-All Blacks.

Former All Blacks and Warriors team doctor, John Mayhew, told Mike Yardley their legal teams will need to do a lot of work.

“They’ll need to prove a link between the head injury of their particular client and subsequent medical problems.”

John Mayhew, told Mike Yardley what's being said is high on emotion and short on facts.

“There's not a lot of evidence repeated concussion causes permanent brain injury, if the injured person has recovered from the concussion."

Lawyers are expected to argue rugby authorities have known about the risks of repetitive head injuries for decades, but have underplayed them.

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