I was there, Katharine. It was an epic race. From memory, there was only one other runner and it just concerned the big two from a long way out. They went at it hammer and tongs from halfway down the back, both jumping superbly and at high speed. Silver Buck got on top on the run-in and won by (again from memory) two and a half lengths. I was at Liverpool University at the time and saw a lot of racing at Haydock in the late-seventies. In fact, I remember seeing Silver Buck win a handicap hurdle there under top weight and ridden by Michael Dickinson himself. This would probably have been in January 1977 or 1978.
If you've got the Silver Buck book you might be able to check this for me but my recollection is that the Embassy final was run on a Friday, probably in early March, having been cancelled when it was scheduled to be run in January. If my memory isn't playing tricks on me, Decent Fellow beat Sea Pigeon in a handicap hurdle on the same card, receiving lumps of weight, of course.
Finally, I recall seeing Silver Buck beat Night Nurse again at Haydock on a weekday, probably in 1979. I think it was the Edward Hanmer, run in late November.
Silver Buck was a terrific horse, as was Night Nurse.