Cannot remember the date my employment ended in London in 1989!

Before my claim can be processed I am required to produce the date my employment ended at a theatre company in London in 1989. The company no longer exists and I cannot remember the precise date. Could anyone please tell me how I can find out this date in order to move this process on? Surely having provided my NI number HMRC would have a record of this already? Thank you in advance.

Hi,
For guidance on your query, please take a look at the link below.
Get proof of employment history
Thank you.

Thank you - however, that link states that you can get evidence of "You can get a record of the current and past 5 years’ employment using:" Please see my post. I am looking for a date in 1989...so that isn't helpful in this instance. I have decided to write to you stating that it isn't possible for me to do this as I do not have a P60 so I can only make a best guess at the date/month. I can only hope that this is acceptable.