I just want to point out that, contrary to many sources, that fuse does not affect turn signals or brake lights.
Just dash, tail and parking lights.
Piggott stated a fuse was added for brake lights, but he was mistaken.
A correct description can be found in Practical Hints, along with the (Lucas) rating of 25 amps. An AGC 10 seems to work fine for me, even before I started converting to LED.
PS TS39781LO had that fuse originally. I added one to TS13571L, but it didn't have it originally.