According to google 50mm is equivelent to 1/0 AWG .
50mm is the cross sectional area of each conductor
I've copy/pasted from google a statement about 50mm flexible tails , IE a single conductor, The SWA armoured cable has 5 of these conductors
50mm Single Core H07RN-F Cable is a form of electrical cable that has a rubber sheathing, making it very flexible, therefore making it perfect for almost any installation. The size 50mm refers to the cross-sectional diameter of the core, the overall diameter of the cable is 17.2mm
17mm is equivelent to 11/16 inch
I shall grab a picture when the off cut comes back to base as my lads are continuing the install whilst I repair appliances