Confidence: It's likely to be this, but I can't be certain.
Notes: Possibly Apamea epomidion (Clouded Brindle). This is described as having distinct subdorsal streaks on the prothoracic plate and an obscure dorsal streak whereas your specimen has distinct dorsal and sub-dorsal streaks. ALternatively could be Apamea crenata (Clouded-bordered Brindle). Boths species can be found in larval stage at this time of year. If you still have it you could try breeding it through to see what emerges.