Mr Mercer was critically injured during his 10th TT when he was among a group of red-flagged TT riders who were allowed to travel back to the Grandstand the ’wrong way’ round the course.

At Ballacrye, near Ballaugh, his machine collided head-on with a course car, which was on its way to the accident which claimed the life of Manx TT star Dan Kneen.

The Auto Cycle Union has admitted liability and had made payments towards his ongoing medical treatment.

But the scale of his personal injury compensation, and the issue of causation, has still to be agreed - and the case could yet go to court.

Now a Deemster has approved an application by the ACU for a declaration that any future claim by Mr Mercer arising out of the May 2018 incident should be heard in the Manx court.

The TT rider argues the ACU is liable in damages in respect of its organisation and management of the TT 2018.

Mr Mercer, who lives in Maidstone, Kent, wants the case to be tried in England.

But the ACU contends that by signing up to the terms and conditions that every competitor has to accept before racing in the TT, Mr Mercer accepted a clause agreeing any claim made by him should be heard in the Manx court.

But the rider’s advocate Damian Molyneux argued his client was not bound by the terms of the contract.

Other riders filed witness statements that they were unaware of the conditions of racing set out in the regulations.

But in a judgment handed down this week, Deemster Alan Gough ruled that Mr Mercer is bound by a contractual term to litigate this matter in the Manx courts.

He said whether other riders had read the terms and conditions was not relevant and he had no reason to doubt that Mr Mercer received the regulations and signed that he had read and understood them.

Deemster Gough said although a claim has not been filed either in the English court or here there has been a claim admitted as to liability and interim payments have been made by the ACU or its insurers to Mr Mercer.

He said it was necessary to move this forward so the appropriate court can consider the remaining issues of causation and quantum before ’memories fade, witnesses become unavailable and other negative circumstances intervene’.

Deemster Gough said both sides were entrenched on the issue and if Mr Mercer filed his claim in the courts of England and Wales, a jurisdictional challenge would inevitably follow.