Well, leaves and wet rails do bring some steam locomotives to a standstill. The steep grades in Devon and the famous Lickey Bank to name two places. That's why steam locomotives needed banking engines to help push. Somevisitng locomotives to the Dartmouth Steam Railway (Paignton to Kingswear) often have failed to make the steep climb from Goodrington (sea level) to Churston (200ft. asl) - usually those from the former Southern Regions - SPAM cans for instance. I know this is genuine - I saw it!
The continuation is Part 2. The tank engine name is Goliath!