It would have been a mistake by customs.
From what I recall two tone airsoft guns should only be available to those over in the UK who are not Ukara certified. Sorta kinda how it works in Canada, if you want a full black airsoft gun, using the ASC AV is the way to go. If you live in the UK if you want a full black gun then you have to be Ukara certified.
"Its only a little bit on fire"