Some excellent posts above thank you. I do have a concern, most here seem to think in military terms about projects and accept they take years and along the way are bound to meet problems for a variety of reasons outlined above. Politicians do not think along those time scales and the impression I get is that taxpayers/voters and politicians are losing confidence in the whole idea or way in which the UK hopes to project power and influence.
Many are deeply suspicious of military adventures abroad, do not want to see anymore personnel coming home in a box and are weary of project cost overruns for systems which are viewed as unnecessary or anachronistic. While much of this is directed at Trident, the Carriers and the F35 are perhaps a close second and the comments directed at the MOD this week by the PM suggest she is rather angry or exasperated about demands for more money.