Choosing a global network of fortified naval bases

If Britain could choose a handful of heavily fortified naval bases, which locations would best protect its global sea routes?

Use Gibraltar, Singapore, the Falklands, a Caribbean-edge island, and Chagos to cover major gateways without creating oversized or easily watched bases.

The proposed chain combines Gibraltar and Singapore with the Falklands, an island near the edge of the Caribbean, and the Chagos archipelago. These positions cover the main approaches to the Atlantic and provide a route across the Indian Ocean to the Far East. A Caribbean base on the edge of the island chain gives ships more approach routes than one deep inside it, making submarine observation harder. Small islands also limit the land area that requires fortification and the population that must be supplied. Gibraltar is preferred to Malta because it controls the Mediterranean entrance and is harder to isolate. Smaller supporting facilities would supplement the major fortified bases. Ascension is useful in that secondary role, but its water supply limits the people it can sustain.