I also tried to key this one (and compare with my own material, photos on the internet...). I think it's either Virgichneumon or Cratichneumon. But there are several species that are not included in Perkin's key that can be found in Scandinavia (I do not have the descriptions of these species, take a look at Virgichneumon at artsobservasjoner.no, two species not known from Norway have been posted here, V. extremator and V. krapinensis, ID by J. Valemberg). I get to Virgichneumon monostagon in Schmiedeknechts' key, but size is too small (should be 13-15 mm for monostagon according to Perkins). None of the keys I have mention number of segments for the flagellum or anything about tyloids for V. monostagon males.
Another key that was recomended by Matthias Riedel is Rasnitsyns key from 1981 (in Russian). I don't know where to find it... (maybe it would help out with the missing species in Perkins?).