What is that fuse? Can someone identify

[ProDave]

Totally random picture thanks to google of a typical DNO supply head The fuse in this one is in the left hand bit where the red wire comes out, but there are many many different variants on this so yours may not have been the same as this.

 

[Andy™]

The whole point of a consumer unit is to provide circuit protection so no circuit can be overloaded, the protective device will trip first. Clearly that did not not happen.

doesn't need to be overloaded or fault current to start a fire

 

[ProDave]

doesn't need to be overloaded or fault current to start a fire

Indeed faulty component or faulty assembly, but those that make the rules thought they would solve the problem by putting it in a tin box to contain a fire, rather than improving the components or assembly to prevent a fire. As I have said before.