[Thanks to Richard Hayes of Devon Law Centre for providing this case summary]
The EAT (Underhill P) has handed down its decision in Northamptonshire County Council v Entwhistle , which is authority for the proposition that it remains reasonably practicable for the employee to file their unfair dismissal claim within the usual time allowed (now three months from the effective date of termination), even though their employer has mistakenly advised them that the time limit for claiming unfair dismissal ran from the date of the rejection of their appeal. This was because the employee's solicitor should have known the limitation date (which ran from the date of dismissal) and filed the claim in time.
Dedman v British Building and Engineering Appliances Ltd  ICR 53 and Marks & Spencer PLC v Williams-Ryan  ICR 193 were correct. Unless the adviser was misled as to the correct limitation date by inaccurate information from the employer, the employee's only remedy was to claim damages in negligence from his adviser.