"Sorry, got to ask, why as an island nation do we need a worldwide maritime defence capability"
Because we are utterly dependent on seaborne trade with the entire world. Cut off the trade links across the Channel and that would be a minorr inonveniencs, the bulk of our supplies (ie food fuel and everything you buy) comes from farther afield, all the way out to the Pacific. Go to Southampton or Felixstowe docks (the two largest container terminals in the UK) and take in the scale of goods being imported. Churchill was only afraid of one battle in WW2, the Battle of the Atlantic, because he knew if our supply lines were cut we would have to capitulate in a few months at best. The situation hasn't changed, indeed it is much worse now. Every now and then I hear people bady about the phrase 'Fortress UK' as an allternative defence posture. Madness. If you don't secure our Sea Lanes of Communication (SLOC) then you have already surrendered. Fortresses. Great idea. Why did we stop building them? Because they were easy to defeat. Lay siege. Defenders run out of food. Surrender.