I agree with Aussiemum, too.
I also feel that although we won't lack the "knowledge" to re-start mills and plants that have been abandoned for years, the labour force will have gone.
In my direct experience, sons have gone to work with fathers and other family members for decades in Port Talbot (and probably other heavy industry towns, too). The majority of the jobs in these plants are NOT cushy numbers. There's no sitting around at a desk, playing games on your phone or Solitaire on your computer. These are hands-on, heavy-lifting hard physical jobs and they're not for everyone (anyone who has seen the film, One Chance, with James Corden as Paul Potts, will see that he felt he wasn't cut out for the job).
To throw younger men with no experience of the job (even from tales of what the place is like from family members), will be too much of a shock for most men to even finish the training. Over the last few years, we've gone from a "family first" system of employing people with family at the plant, to employing via agencies. Depending on what part of the plant they're sent, some of these agency recruits have failed to last the first day. They take one look and don't come back. The machinery and conditions are overwhelming and intimidating.
These jobs aren't the kind of jobs someone fresh out of an office/retail environment will take to like a duck to water, no matter how much training they're given.
Bill - you seem to be trying to say that because the job isn't technical, any idiot will be able to just pick up where the jobs were left. Well, the guys working there now aren't idiots - far from it. Because the majority haven't had the opportunity or inclination to go into further or higher ed, does not make them stupid. They're trained on the floor for the job they do. And most of them do it extremely well, under difficult conditions.
On top of that, you have the shift work needed to keep the operation running 24/7. This also sorts the wheat from the chaff. The younger/newer agency recruits aren't fond of giving up their Saturday nights out and think nothing of pulling a sickie due to a hangover or a big sporting event. At the moment, the shifts are covered by men who are used to working this shift pattern (12 hours nights and days - they're killer shifts even if you don't take into account the physical conditions. No wonder they say shifts take 10 years off your life. I'd say it's more!).
If we leave the industry go, our labour force will be too soft to want to work at plants like this in 10-15 years time. We're already importing labour to work the jobs no one else wants to do in this country, and these people are unskilled so easier to find. Good luck with finding a reliable, hard-working labour force when the jobs are forgotten.
BTW, several different grades have been made this week alone. At Port Talbot, despite out-dated machinery, they're still fulfilling orders and can swap grades in hours. Surely this is the kind of steel manufacture we want in this country - any type ordered, and not being hobbled by one grade per plant?