Age UK might be able to help. https://www.ageuk.org.uk/information-advice/money-legal/pensions/tracing-old-pensions/
From what he says he doesn't need it tracing, he knows who holds the records but they won't deal with him unless he provides his pension scheme number.
Thanks for your reply.
I am unable to remember my works number. Air Products claim to only have records going back to 2008. I do not believe them.
A works number isn't compulsory but it might have helped.
The point is that there's a pension pot which relates to you & apart from the pension number the records will have your name, date of birth & address at the time it was set up so it's impossible not to be able to trace your pension records or to confirm who you are.
My wife worked for Philips in the early 1990's for just a couple of years but she accrued a small pension pot which was transferred to a firm called Pension Insurance Corporation when it had been dormant for several years.
Pension Insurance Corporation are closing all dormant pension accounts & they asked HMRC to pass on a letter from themselves about her pension.
They included a 'lost details' form which she had to complete to say she didn't have any copies of her pension documents.