I have many memories of that weekend.
If I remember correctly one of the mechanics looking after Jochen Rindt that day was Jim Pickles who during 1970 was generally looking after the GLTL F3 team of Dave Walker and Bev Bond. Jim was always great to chat with, time permitting, and full of great info that schoolboys like me loved.
The car that Rindt used for the Gold Cup was the one in which he had won the British GP at Brands earlier in the year and, sadly, was the car in which he crashed two weeks later at the Italian GP.
Although Jackie Stewart was entered in a March 701 (which he practiced) the meeting marked the debut of the Tyrrell 001. In the Paddock at Oulton at the time was an old shed and a friend and I were intrigued why Roger Hill (the chief Tyrrell mechanic) kept disappearing into this shed. Peering through the window gave us the answer, the new car.
Stewart started at the back of the grid in the first heat and finished 7th, although he did set the fastest lap. Unfortunately, he didn’t start the second heat due to an engine problem.
Graham Hill also took part in the first heat in Rob Walker’s Brooke Bond Oxo Lotus 72, but retired early in the race with engine problems.
The supporting F3 non championship race was won by future F1 star Carlos Pace in a Lotus 59 from Peter Hanson in a Chevron B17, while Frank Gardner won the Saloon Car race in his Ford Mustang from Brian Muir’s Chev Camaro.
I also recall that at the end of the second heat Rindt stopped his car on The Avenue and nipped up the nearby hill to a waiting plane in which he departed, which explains why he wasn’t on the lap of honour!