Accidentally discovered a better way to bake whole (scaled and gutted) trout today:

Preheat large oven to 50C. Oil the inside of a piece of file big enough to wrap the fish. Put some flavoured butter and perhaps herbs into the fish’s cavity. Wrap the fish up in the foil and bake until the internal temperature reaches 45C (about 30 mins, check after 20 to see how it’s getting on). Quickly remove bones and serve on warmed plates, immediately as the fish loses heat fast!