Well, thanks for all the comments and helpful advice! The slightly longer story is that as a then 70 year old driver, my obligatory licence renewal was delayed for a year by covid back in 2020. Not having received any reminders from DVLA since then, I unwittingly allowed my licence to elapse. . . until now, that is. The good news is that I've now spoken to someone at DVLA who has asked me to send in a completed D1 licence card renewal form (plus new photo) via the post office, which will then be validated. Meanwhile, because my licence has already been updated 'in absentia' (so to speak) I'm still free to continue driving, despite having an out-of-date licence card. It also means that my driver's insurance remains valid.
I mention all this just in case there are others out there who are wondering what their own legal status might be in the same or a similar situation. Thanks again for all the helpful comment. Much appreciated. GeeKay.