burnt out wire in cooker switch?

Whilst our double electric range cooker (Britannia) was on the other day there was a loud noise and then the cooker stopped. We could smell burning. The live wire into the cooker switch, on the cooker side has burnt out and the sheath melted and the connection blackened where it connected to the switch. The fuse did not blow in the CU.
It all appears to be wired correctly from the cooker to the switch.

Is this likely to be a switch problem or a fault with the cooker?