The right wing of the Tory Party will bring down this coalition & cut David Cameron's throat without blinking as soon as they think it might provoke a general election which they can win & only they can afford. The leaked [how convenient] letter from Liam Fox could be viewed as a first opportunity & skirmish in this process.
In truth the country does not need any form of Trident replacement. Since we can't fire the missiles without approval from Washington it was arguably a nonsense when it was first built all those years ago.[I had some minor personal involvement in those days]. We don't need tranche 3b of Eurofighter - nor does BAE Systems. The future is Unmanned Ariel Vehicles (UAV) & BAE is putting huge effort into those (just as Fylde LibDems were arguing they should during the 2005 General Election). The CVF Aircraft carriers? Well as an island nation we do need to be able to build big ships but it's doubtful if these are the right ones. I have been following the progress of these vessels through the politics, design & procurement for best part of five years & to be brief they are already massively over budget & years behind schedule and have serious questions about endurance.
If these 'ego polishing' projects were cut or massively re-worked, combined with pruning of the hugely overweight MoD Civil Service and Senior Officer ranks, there would not be a need for more defence cuts. Indeed it is probable we could give more numbers, equipment & support to the 'poor bloody infantry' that are so marvelously doing the last Labour Governments dirty work on the ground & still save a stack of money.