Just noticed a brief mention of Gerry Marshall and Old Nail in the Winter 2009 issue of Vauxhall Magazine:

"Vauxhall's involvement in saloon car racing stretches as far back as the Sixties, when the late Gerry Marshall drove a Viva GT to second place in the Redex Saloon Car Championship in 1969. The Seventies, too, were productive. The Firenza, affectionately known as the 'Old Nail', holds the record for the most saloon car victories in the UK and is displayed in the Donington Museum."

There's a couple of pictures of nail as well.