I think caravan wiring installers, do a special course, in hiding the main fuse.....there is convention in fusing caravan batteries.
That is to fit the single fuse in the positive feed wire from the battery as close as possible to the battery.
Look for wires from battery terminals entering caravan at the back of the battery box.
Locate this entry point inside caravan ....follow the wires looking for a fuse.....usually a blade fuse.
This should be within 0.5meters and often obscured by other fittings and components.