There is a well known colony of these snakes around the Welsh Mountain Zoo at Colwyn, following the escape of a gravid female snake, over thirty years ago. Rumors of a second UK colony were fuelled by the recent reporting of a 'strange grass snake' found close by London Zoo.
We can now confirm that there is very probably a breeding colony of this pretty snake in the centre of London ! The picture below is of a sub-adult found at the site. This snake was only 2 feet long; adults can grow in excess of six feet, and are strongly arboreal in nature.