The UK became a 'petro currency' from about '84 on, by '91 more barrels of oil were annually coming out of the UK North sea than out of Saudi Arabia. This jacked the currency up to the point that it was impossible to manufacture here to economically sell abroad. The home market was not big enough to sustain Hymac, Priestman, RB, etc. It is a pity there was not only just enough oil for our domestic needs. This though was the cookie jar politicians could not leave alone. Oil works for Norway & up to a point for Saudi, but not elsewhere. They drilled the Falklands till it was like Swiss cheese hoping to announce a second golden age of prosperity, but found little. So the party is now over. Note that Sheffield Forgemasters was nationalised the other day to keep it alive. This would not have happened even a few years ago.
Pity because the design capability of Priestman was good, look at the unique VC15 - Can reach further & boom lighter than conventional machines. One of these was repaired at Threlkeld & put back to use down south. Another was rebuilt in Vancouver & put to use. They also
designed a knee action face shovel in the 70s. The past is another country, they do things differently there.