About 20 segments, 2 pairs of legs on MOST segments, 10mm long, brown legs, found outdoors in soil.
No interactions present.
There are several flat-backed millipedes. The ones I find are always Polydesmus, can't remember which species. You really need to look at the genitalia on the underside of a male to identify them.
John is quite right to warn that these are tricky to identify, but if your size measurement of 30mm is correct then there are only two species to choose from I think: Polydesmus angustus or P. coriaceus. Of these, P. angustus is more likely, on the grounds that it is the commoner of the two and ranges further north, but I can't confirm it from the photo.
Brachydesmus superus is not supposed to grow over 10mm long. What size are the squares in the background of your photos? I count about ten squares for the length of this millipede, which means that if it is 30mm long each square is 3mm, is that correct? It's a great idea to photograph it over the squares so we can get a good estimate of the size!
Entomologist and biological recorder
Dear Martin, sorry! We got the measurement wrong, each square is one mm long, not three!
Oh well, never mind! I'm afraid that means there are several species it could be, so we'll have to stick with identifying it just to family Polydesmidae.
Lat/Lng: 53.465066866632, -2.2487149536937
OS grid ref: SJ835965