Earlier quoted context omitted.
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.
If there is a large war, those countries will prioritize domestic consumption and the UK will immediately stop being able to produce weapons. Domestic steel production is an essential element of being sovereign, as opposed to being the handpuppet of a larger power (like the US).
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.
There is actually a really high quality government review of the whole subject: https://assets.publishing.service.gov.uk/media/690b868714b04...
Lots of discussion of moving to EAF/DRI from traditional blast furnaces.