Half of all steel in the UK is imported anyway, and there are many places to obtain it. Unless the UK goes to war with most of the world at the same time, it’s not going to have trouble getting steel.
Now check where the inputs to steel production come from.
The UK built a lot of refining to use local iron ore and coal deposits. It used those deposits. They are now substantially used up. Subsurface mining is uneconomic, and open mining is politically unthinkable.
Britain's last two territorial conflicts involved the Falklands, and Icelandic fishing ships in the neighborhood of Rockall. I don't recall that third party assistance was required in either dispute, thank you very much.
The US the other hand is always asking for other countries to bail it out of some mess or other.
Did you miss the word "large"? And the UK required significant US assistance during the Falkland Islands war, so apparently you're quite ignorant about history.
The command and control systems are American. The intelligence network is American. The last time the British military acted without US support was Suez. The UK went in on NATO 100%.
France took an entirely different set of conclusions from Suez.
NATO can and probably would shoot them out of the sky using ballistic missile defence. IIRC Britain has a total of 8 missiles.
Britain's obsolete Trident subs are manufactured by Lockheed, so if they fall out with Trump they will lose access to spare parts. The replacements aren't due until 2028.
Really? There is a large war going on right now and the key material is chips. Drone don't use a lot of steel, neither do missiles or modern airplanes.
Yes you need artillery and particularly shells. But you are so much more limited by the capacity of your munition factories that how much steel you have would not be an issue. One of the main things you would need for a new munitions factory is trained workers.
The World Wars were wars of mass mobilization and industrial capacity. People went into the first thinking cavalry was important, the second thinking battleships still mattered. My point is I have no idea what the next great war might be like, but thinking the winner will be who chugs out the most tanks in five years may be looking in the rear view mirror.
You can't occupy territory with drones (yet). You will need people and moving people in a drone-infested environment will mean protecting them with armoured vehicles. Yes, these vehicles will need enhancements and other new tech to counter drones, but armoured vehicles aren't going away (MAYBE the tank's days are numbered, though).
If you are really interested in this, I highly recommend subscribing to war on the rocks. Their articles and paid podcasts have legit defense industry people publishing studies on this subject. https://warontherocks.com
It's a myth that battleships didn't matter in WWII. They ended up being critically important in the Pacific Theater for carrier escort and amphibious fire support. They didn't stop mattering until the widespread deployment of guided missiles and other precision munitions.
Domestic steel production is an essential element of being sovereign, as opposed to being the handpuppet of a larger power (like the US).