In my comment, I try to think of a position between yours and that of Barclay.
If an organization can be certain that it has captured business email correspondence from one person to another system, it can proceed with automatically deleting email from the account. However, if it cannot be certain that it has adequately captured business email elsewhere, it should not proceed with the automatic deletion of email from the person's account (and especially not if the person has a role of historical importance).
I am concerned that automatic deletion of emails appears to be unrestricted in the UK government – it does not depend on whether emails are adequately captured or not.
