>I remember my Dad putting tin-foil around the fuses
The fuse is the weakest link in the circuit.
If something goes "wrong" with a device (iron or whatever) then it is the fuse that blows (being the weak point).
Putting silver paper round it just STOPS it being the weak point and makes some other part of the circuit "blow" (the iron perhaps).
If the device (like the iron) has metal components, and faulty wiring has made the metal live, you could kill yourself by putting silver paper round the fuse and touching the iron.