Arnolt Bristol

According to the programme of the event car number 20 in  the 'Guards Trophy GTSR Race', race 6 of the Gold Cup meeting at Oulton Park in August 2008, was a 1953 Cooper Mk1 T20 driven by Ed Cottam of Fareham. Here's the car in the paddock and it's obviously not a Cooper T20:

It's an Arnolt Bristol from the early 1950s and you can read what www,classicandperformancecar.com says about it here.

Here's Ed Cottam at Lodge Corner during the race