I think 'defence of the realm' springs to mind! The original idea was to protect the U.K and the Commonwealth. The commitment
to NATO has somewhat changed since the Cold War defrosted.
However places like Zimbabwe need regime change and re-entry into the Commonwealth . There are two big problems 1. No oil there and 2. Bush cannot find it on the map let alone spell it!
So it isn't going to happen - we need an outbreak of ethics.