Probably European law now that forbids it. No longer have Crown immunity either, although not sure how long ago that changed. The only time you would pay money is if you leave before the retainment period for taking a commitment bonus. For techies it was reduced from 12 months notice to 6 in the last couple of years. Mind you, a lot of us will just end up serving our 9 years and leave as there's no longer a guarantee of being signed-on, and there's not a lot of space now to promote into. Of crouse, the MOD will be too short-sighted to see the problem this will cause 5+ years down the line (again)...