Ken - the numbering of all my images is: year (175 = 1975) Month (08) day (24) and either a sequence, film number or car number.
So Tony Brise was demonstrating the Embassy/Hill 24th August 1975. Mallory Park.
Not sure which car it was. Was it the latest Hill (GH) or an earlier one? I'd be surprised if they thought it was worthwhile firing up the latest F1 car for three demo laps.