[Major Tom]

If that's the way Marshall does it, that's not a very good way (IMO) to do it. But it probably does cut down on the number of incidents where stubborn people who know very little about electronics just go and defeat the fuse, frying their transformer or some other valuable part.

Since fuses rearely blow unless something has gone south internally, that probably is a wise move on Marshalls part. It is just too easy for someone who doesn't know any better to put a higher value in there, or wrap aluminum foil around the bad one. Its been my experience that a large portion of the population does not know any better.