Dave Reader found this clip of the London Cross Country Championships on Hampstead Heath.
The athlete is Graham Taylor and he ran 1.39.46 in the Belgrave 20, his best time for the marathon was 2.19 when he ran a 64 sec last lap in the Poly Marathon, which I think was the trial race for the 1966 European Champs in Budapest. He overtook Jim Hogan on that last lap , who went on to win the European title looking around all the time thinking Graham was going to do the same thing to him. Unfortunately Graham was ill before the race and could give of his best on the day.