No interactions present.
Looks more like Limacus maculatus, but I'm not good on these two similar species.
BMIG website: www.bmig.org.uk (centipedes, millipedes & woodlice)
BMIG Newsletters ~ www.bmig.org.uk/view/resource/bmig-newsletter
BMIG Bulletins ~ www.bmig.org.uk/view/resource/bmig-bulletin
I agree Steve, looks like the Limacus maculatus i find in my neck of the woods.
Lots going on under those logs, the other slug looks like a possible Lehamannia valentiana (now had a name change to what i can make out is Ambigolimax valentianus)??
It's mostly (almost always) L.flavus where I live. However, I found L.maculatus in Oxford city this year and, judging by what has happened elsewhere in Britain, it may spread.
I agree other slug could be L.(now Ambigolimax!) valentianus (pinkish with dark stripe).
Lat/Lng: 51.753, 0.46
OS grid ref: TL698088