Today, 28th Feb 2022, I have received a letter from the Chief Ombudsman to say that he has decided to investigate the complaint and has now begun making enquiries with the Ministry's Chief Executive.
In the latter half of last year, I was asked for some additional information by the Ombudsman's Senior Investigator, which I supplied. I gather from this letter that they have now concluded the situation warrants a formal investigation and ruling. I have not been given any indication how long this is likely to take, other than "We will write to you again shortly."
Updates when they are available.