It's easy for him to do: make the purchase of the Trident replacement (approx cost GBP 100 Billion) part of the defence budget. That way he can reduce the Army to 3 CCF detachments, the RAF to a small glider club outside of Northampton and the Royal Navy to four dingys in Poole Harbour, while at the same time claiming to have significantly increased defence spending.
It`s probably because most of this likely horror scenario was already widely trailed in the quality press this year. With headlines in the Times, Telegraph & Guardian as recently as early March talking about regular army numbers potentially down to 50000. This was based on detailed research work by RUSI which highlighted the fact that, whatever way you played out the defence figures, one way or another, their conclusion was that further army cuts were going to be inevitable after the election, unless something really fundamental changed.
So yes, there has been a fundamental change, no coalitition & a Tory majority which, if anything, other than trident of course, means presssing ahead with more of the same bad news for the defence budget & the regular forces in the defence review due out this October..