If that fuse box is fed from the other side of the car, at the starter relay/solenoid, do put a fuse or circuit breaker in line just after the relay. I did this on my 4/4 after finding that feed is unprotected.
What amp fuse do you use in that Graham?
"Y mae dafad ddu ym mhob praidd" 1972 4/4, 1981 MGBGT, 1984 FLHT1340, 1980 XLH1000, 1990 ZX10