Our home meter failed and, after a 3-month wait, it was finally replaced today. Whilst he was here, the SSE electrician thought he'd inspect the fuse. After breaking the cover of the fuse holder, he discovered that the link was a solid "tube" of metal. The holder clearly wasn't meant to be opened. He replaced it with a 100A fuse in a new fuse holder but was a bit perplexed. He contacted a colleague (of 20 years experience) who seemed equally perplexed.

Anybody know anything about the original "fuse"?

When we recently had major problems with our electrics, the electrician opened up our "main" fuse and found that it had blown at some time in the past and that someone had bodged it with some steel wire. Although it was clearly a replaceable part, it took home half a day to track down a replacement. By all accounts it takes a pretty major event to blow one. Ours was 60A, not 100 though.
My guess is that these days the RC circuit breakers render the main fuse redundant. Then again, as you may have guessed, I'm no electrician.

The fuse is there to protect the suppliers cable, not the dwelling. This fuse is always the property of the electricity provider though, not the householder. This would be why the electrician is perplexed at finding something other than a fuse in there. It is not uncommon for the providers to prosecute home owners if this fuse is found to have been tampered with or had the seal removed.

The fuse would normally be a 60A but the electricity provider could have fitted or replaced with an 80A or 100A fuse.

A problem often exists when properties are extended or changed into HMO's. The supply SHOULD be checked and if found to be insuficcient it should then be upgraded. However the cost of upgrading a supply can be hugely expensive. Some developers may choose to try and ignore this element, or worse still replace the fuse with something less likely to blow!

Yup - which is even more odd that it's the supplier's electrician that didn't understand what's going on. In place of the fuse was a "solid" lump of metal in a proper sealed holder. Nothing that would have fused in the event of a fault (unless there is some cunning material that I've never seen before). The house is about 12 years old and the supply hasn't been touched in the 10 years we've been here.

These are the usual UK Standard domestic fuse types.

From how you describe the item it sounds like a surge protector or neutral link but they are usually HUGE

Yes - this thing was pretty big - 25mm dia and around 50mm long at a guess. Held in a large two-pronged holder which was marked up at 415v.

Some cutout fuses look like this

Then the prongs clamp onto the metal ends

Are you saying the ceramic bit was missing and replaced with metal tube probably 25mm conduit?

that fuse is to protect the tails to the meter consumer unit

Is the cutout rated to 100 amps not all are some are smaller

There are that many sub contractors carrying out work now, nothing would surprise me any more!

If you imagine one of those fuses except made of steel rod bored through the core then that's what it looked like. Except that it was housed in a proper commercial sealed housing. I have no doubt that it was a proper component but whether it's a dummy or what I don't know.

Is this anything like it best pictures i could find on the net without spending ages, the fuse previously linked should go in something similar to this

Like this

This is what they look like inside best picture i could find

Top left with the tags secured to the fuse before being sealed in the fuse holder

So it looks exactly like that except the bit inside was a steel "tube" and the case was riveted shut.

Hmm can't say I have come across anything like you have described but then I don't deal with cut out issues very often and when we do we just ring the relevant network to sort out and to be honest it is very rarely blown fuses and usually cable/joint faults!

Is it possible that the incoming mains cable comes from an accessible distribution point outside of your dwelling, and that it may be fused there, and that the rec cut out inside your house is merely used as an isolating device to terminate the incoming split concentric cable to the meter tails, if not it's a shocker ( no pun intended ) as the fuses at the substation are around 400amp rated