Are we reading the same OP? Eric said that the plug was marked 5A, and explicitly stated that it said nothing about fuse rating:The OP is refering to moulded plug MARKED 5A fuse. Not a rewirable 13a BS1363 plug.
I found a BS 1363 plug well marked 5A with a lead marked "XD RVV WGX3C PVC WIRE GP" and a socket marked "KKS 10A KKCK" an IEC 60320 C13. It does not say 5A fuse fitted ...
Kind Regards, John