MOTOR ACCIDENTS — application by defendant in the course of the trial for the plaintiff be re-referred to MAS for re-assessment as to the degree of permanent impairment — s 131 of the Motor Accidents Compensation Act 1999 is a gatekeeper provision and the power under s 62(1)(b) to re-refer a plaintiff to MAS is not available at the instigation of a defendant once the threshold for damages for non-economic loss has been satisfied — a plaintiff who has not yet satisfied the threshold is never precluded from crossing that threshold and may be re-referred at any time