Remember the PM is instituting an anti-terrorist and homeland security revue, not a Defence revue.
Is it conveivable that the Armed forces could be realigned as homeland security services?
Lots of light grey armed coastal defence vessels and revenue cutters?
Airport perimeter security, armoured cars and all?
Event cordon parties?
Random checkpoints for ID checks?
Dockland patrols?
Our present armed forces would protest but in time you would still have shedloads of volunteers for the motherland security service.