A ring main is all well and good protected by a 32 Amp MCB until someone breaks the ring meaning two legs of 2.5mm are protected by 32 Amp. As 2.5mm twin & earth ranges in current carrying capacity around 19 to 28 Amp depending on the type of installation. This is changing the theory as the fuse is the weakest link to the cable is the weakest link. Or connect me if i´m wrong