Peter.h, it makes no difference to Vieux Lion Rouge being the “winner”, but I get 244 fences for Amberleigh House! In order from the oldest race, my counts are 7 (then brought down), 22, 18, 22, 30, 21 (one fence omitted due to low sun), 30, 22, 30, 22, 20 (then pulled up). Happy to be corrected if this is wrong.
I also wondered about Manifesto and Big Fella Thanks as contenders for this title, but their counts are both considerably lower. For Manifesto I’m basing this on his Grand National record only, and do not know if there was other racing over the National course in his era (1890s-1900s).