an exstinct Butterfly was spotted near London the Butterfly Conservation Trust say it might of been released
https://www.bbc.co.uk/news/uk-65804939
Yes the black veined whites wouldn’t of been released from anywhere in the UK cause there completely extinct so it could of been someone from outside of the UK or someone that happened to have them and decided to release them. I cant say weather it was for certain or not but cause there’s none in the UK it’s a possibility. Maybe someone brought them over from a different country for example or they had reared some where they do exist then decided to go near London and release them Its good it’s not native but usually with releases they should be planned out So weather they breed or not is hard to say but if there have been attempts to bring it back in the past they havnt been very successful cause there still exstinct