No KKOB, you probably wouldn't tell them.
However, as although DonM can apply online for a new licence, a form would be sent out for his signature - it looks to me as if he will have a real problem. It maybe that a reminder is sent two months before the expiry of his licence (as it does when one reaches 70) In which case he could apply online and when the form arrives for signature there would be plenty of time to get a relative to send it to Turkey by one of the secure services, sign it and return it to a member of his family or direct to the DVLA.