They must be in a short/petite length, in a size 18, and not too low waisted.
When I was a smaller size I had some from Montane, but their thighs aren’t generous enough so I found them too tight when climbing over stiles etc, and anyway they only go up to 16.
I got some from Craghoppers and they do fit better, but they have a 2000s-style low waist so they keep falling down no matter what size, even with a belt.
Any other suggestions please? Not many companies seem to make petite length trousers in a size 18, and I’m pear shaped so the waist does need to be high enough.