No interactions present.
These species are easily confused:
Arion (Arion) ater Large black slug
Arion (Arion) flagellus Durham slug
Arion (Arion) rufus Large red slug
Arion (Arion) vulgaris False Lusitanian slug
For a key (where Durham = flagellus and lusitanicus = vulgaris) see
To be sure, it is necessary to examine the spermatophore and genital anatomy.
thanks very much for your link - very useful explanation.
Lat/Lng: 53.6, -1.9
OS grid ref: SE1222