If you want it to be able to carry 13A, 1.25mm² is the very smallest you can use, but 1.5mm² is preferable (or, obviously, larger if you wanted!).OK John thanks again ... Regarding my making of extension lead what is the best cable to use for the 13amp plug? I take it 3 core flex with a minimum of 1mm wire or any 3 core flex above this size wud do?
Kind Regards, John