It's a common garden slug I believe, usually seen in black - but it does come in a variety of colours.
Found this on the Conchological Society of Great Britain & Ireland website
Arion ater (L. 1758) Description: Very large slug. Extended length 10 - 15 (rarely 20) cm., and contracts into a hemispherical attitude. Very variable in colour, completely black specimens being commonest in north of range, but also brick-red, orange and grey. The foot fringe is broad and often paler and redder than body. Dark lateral bands are usually present only in small juveniles, but occasionally persist in adults. Tubercles large and elongate. When contracted and irritated, may rock from side to side for some time. Habitat: Very ubiquitous - grassland, moors, hedges, woods and gardens, even on the most acid terrain.
Hope this helps
Karen
The greatest glory in living lies not in never falling, but in rising every time we fall.
Hiya Happy Hippy,
Thanks for the quick reply, a common slug you say, well it made me take a double look when I saw it, it's a very unusual slug around my district and we were concerned that it was a new visitor perhaps from afar, however panic over and thanks again for the information.
Unknown said: It's a common garden slug I believe, usually seen in black - but it does come in a variety of colours. Found this on the Conchological Society of Great Britain & Ireland website Arion ater (L. 1758) Description: Very large slug. Extended length 10 - 15 (rarely 20) cm., and contracts into a hemispherical attitude. Very variable in colour, completely black specimens being commonest in north of range, but also brick-red, orange and grey. The foot fringe is broad and often paler and redder than body. Dark lateral bands are usually present only in small juveniles, but occasionally persist in adults. Tubercles large and elongate. When contracted and irritated, may rock from side to side for some time. Habitat: Very ubiquitous - grassland, moors, hedges, woods and gardens, even on the most acid terrain. Hope this helps Karen