Britain is no longer famed for it's military, but it is famed for the military
prowess it possesses.
Britain isn't big enough to fight a war on it's own, so it needs support in the form of (Usually) lots and lots of American manpower. Or, conversely, the copious American manpower needs the proficiency of the British support troops. We're the go-to guy for military support, since our units are so highly trained and equipped. Well- that was the plan anyway.
We're kinda like the Eldar.
Why the hell does everyone keep citing history here.
The question is
CAN Britain be invaded. Not
WAS Britain invaded. Times, strategies, and armies have changed
significantly since 1066, Saxon invasions, WWI, WWII and so on.
Nothing is the same since even WWII, so you can't cite them as some kind of precedence that we'll be invaded.
On a lighter note, don't you just love this:
Wikipedia Challenger 2 Page said:
Crew and accommodation
The British Army maintained its requirement for a four-man crew (including a loader) after risk analysis of the incorporation of an automatic loader suggested that auto-loaders reduced battlefield survivability. Mechanical failure and the time required for repair are prime concerns. A human loader is able to maintain a higher rate of fire than is possible with current auto-loaders, and can assist with maintenance of the vehicle.
Like every British tank since the Centurion, Challenger 2 contains a boiling vessel (BV) also known as a kettle or "bivvie" for water which can be used to brew tea, produce other hot beverages and heat "boil-in-the-bag" meals contained in ration packs. Most other British AFVs also have BVs.[7]
This BV requirement is general across the board for armoured vehicles of the British Armed Forces, and is one such requirement almost unique to the Armed forces of the UK.