It is clear that a number of Contributors, here, are convinced that the only armed conflict we may be engaged in over the next 15 (ish) years will be against fanatical tribesmen in some (largely) landlocked s**t hole. There is no useful arguing with that mindset. They are convinced that if the unexpected does happen, we can buy the necessary missing asset off some obliging “shelf”.
We have, like it or not, obligations to overseas Dependencies and those that fall to Permanent Members of the UN Security Council. We also have National interest in natural resource assets in far flung places. Additionally, over half of our foreign trade is outside Europe and involves transport either on or over the high seas. A defence Force centred on even the best equipped Army on the planet would soon become very wet and very dead.