A hidden danger which can occur with the brown bakelite fusewire holders.
The coloured dots on the back of Wylex rewireable fuses are not just there to indicate the fuse ratings. They actually cover the back of the screws which hold the brass contact blades in place.
If this coloured resin is damaged, the metal screws are exposed - both of these are live in normal operation.
Any fuse with this type of damage must be replaced.
This method of failure isn't limited to just Wylex - many older fuses of similar design from other manufacturers can have the same problem.