As others have said there's a lot to choose from. There have been some high speed runs that I wish I had been on. One of my best moments was on GBIII diverted up the Lickey, with hundreds of folk watching us. But then there was also being steam banked up the Lickey on The Midlander on 11-12-1999. And Vintage Trains' Aquae Sulis on 15-10-2011 when we were given a clear road through Swindon through to Foxhall Jn. That was also the last time I travelled with a friend who is now deceased.