Mmmm, it has been £660 max for a long time now, at least 15-20 years.
I do recall a few years ago there was discussion ongoing at Veterans UK (or SPVA as it was at the time), about increasing it, at least with inflation. I bet that plan was side lined.
Could be again time to run it up the flagpole and see who salutes!
Mind you as the current Sec of State has not even get round to tabling the Statutory Instrument uprating all War Pensions in line with inflation for April 2023, don’t hold your breath.