Actually after sleeping on this I see what Andy means - cooker/shower on its own independent circuit is a known load, ergo the cable can either handle it or not. If cable is not overloaded, then MCB / fuse protects against dead short cos that's all you need. Whereas a ring main with half a dozen sockets has far greater potential for overload depending on how many appliances are plugged in at any one time hence cable must be able to withstand full current rating of MCB.
Have to say a cooker I connected recently looked like it was wired in 1.5mm flex as supplied by manufacturer, seemed bloody daft connecting it to 6mm cooker circuit.
Have to say a cooker I connected recently looked like it was wired in 1.5mm flex as supplied by manufacturer, seemed bloody daft connecting it to 6mm cooker circuit.