Black veined Whites suddenly turn up on the edge of London while exstinct. And someone found someone to be releasing Butterflys

Releasing previous known native species is how white tailed eagles got back here.

Releasing previous known native species is how ospreys are now breeding on the south coast. (Ospreys re-established themselves in Scotland but failed to disperse into previous territories).

(obviously the article refers to a possible uncontrolled/unmonitored release)

Beavers have been subject to uncontrolled/unmonitored releases. Which irritates some land owners.

Hugely complex subject IMO.

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 

www.birdguides.com/.../

It ain't the first time (suspected) captive bred insects have been released. Large tortoiseshell occassionally crop up (and seemingly fail to establish).

Graham Smith's observations are well constructed, well thought through IMO (heavy on aspects of the precautionary principle). It also appears that butterfly enthusiasts have their version of 'twitchers'.