That's from the Tourist Trophy race at Siverstone on the 22nd September - the car is a funny Gold colour I think - there is a colour photo of it on the LAT website.
I think Dad shared it with Tim Stock, Brian Atthews and Denis Bissell - I have got the programme and race report at home - the car was entered as a 2.3 Magnum by DTV but it's possible it was Tim Stock's car