There where some short lengths on the St Ives branch, particularly on the short straight behind Porth Kidney sands, between Lelant and Carbis Bay.
I used that line (for the first time) the week before last and I don't remember noticing it, but I probably wasn't paying attention.
There’s a number of short sections on the WHL, including the extension and Oban branches.
...some 45ft? Some of the latter on the Mallaig Extension...
From memory, there are (unless they've been replaced since I last went that way in 2013) 2 or 3 stretches of short rail on the Mallaig line, the first being just west of the head of Loch Eil near where the line starts climbing towards Glenfinnan; there is one on the Oban line (still there in summer 2019), between Taynuilt and Connel. I don't think there's any between Craigendoran and Fort William (parts of which route are now c.w.r.).
I've always assumed these are 45ft, and I'm guessing they're bullhead, but I don't know either of these things for certain.
Not long ago there was some similar rail between Reedham and Yarmouth (starting about 50 seconds into
this video --not mine), but I think the line may now have been relaid.