The ACOC Archive has the following grainy b&w photo published in ACtion of Sept 1988.
The event was the ACOC National Day at Berrow Wood School Gloucestershire.
The wheels, number-plate backgrounds, auxiliary lights, windscreen wiper positions and slightly open bonnet are all similar!
The 2 owners were G Cormack and Ian Clarke. It is not recorded to whom each car belonged. Cormack's car won the Class by a short head.
The event report also records the prescence of Alex Jacob's sole Vintage Six - and one such car is discernible in the background of your much better photo.
Looks beyond reasonable doubt that JLH 182K was the second AC 428 Fastback!
Merry Xmas!
John