The Martin Birrane Kar-Kraft development car which is mentioned above and appears in the photo above from Eric Walker, is in this excellent race footage from Crystal Palace, 1971, which features the epic battle between Martin Thomas in the Camaro, plus Mike Crabtree in the Escort RS1600, and Gerry Marshall in the Viva GT. If you have a spare 20 minutes, I guarantee you'll enjoy this footage, with Murray Walker commentating. Martin Birrane starts off the back, and quickly works his way through the field.