Ron: l now have some details of the mystery Mercury-engined ‘Allard’ Special, currently for sale at Bicester Motor Shed.
Chassis no is H 54 204, and
Engine no: 51221 2. The vendor has owned the special for ‘a few years’, the previous owner owner having had the car for 68 years before that. It is said that during that lengthy period, the car has always had the identity of a ‘special’.
Hope this helps; regardless of its i/d, from the photos at least, the car looks really nice, to me. Tim.