So...
A defence budget that already can't cover its commitments, and is projected to be £36Bn in deficit over the next 10 years.
Massive cuts imminent - announced within months
A government effectively saying we will not be committing to anything beyond 2015 when we pull out of Afghanistan, therefore scope for more cuts from 2015
£20Bn estimated costs (when have defence cost estimates ever been accurate?!) of Trident replacement to be met out of a Defence budget of about £36Bn (over about 10-15 years I'd imagine?). Now I'd guess that the Treasury will not be increasing the defence budget proportionately (if at all!) to cover this new requirement... I also bet that the Government will not allow the MoD to even consider cancelling or scaling back Trident replacement to allow the funds to be better directed to defence capabilities that might actually be used....
Now to me, I'd look at those figures and suggest defence is f***ed. Liam Fox is right to be fuming - he won't have a department left by the time this is all finished! and I thought Liebour were bad....