Scottish Accent

The actor playing the Supt Follands Assistant spoke in a fairly southern/central English accent in the first scenes.. either my ears deceive me but he seems to lapse into a Scottish accent 10 minutes or so in.. then back to his normal accent later.. reminded me of Chomley Warner and Grayson from Harry Enfield some years ago.. maybe I missed a bit where the actual character was putting the accent on as a joke..
Cracking film though, with some then unknown players later to be seen in many British Movies (Joss Ackland etc)