Its about time that the minority of those who are inclined through advanced age to believe that they can do as they wish because they will retain their licences due it 'being their right to independance' are taught hard lessons otherwise and made to retake their tests and be disquailfied until they have.
I had the same a few days ago from two very old ladies who always let every other vehicle coming out of a side road come out in front of them while they persisted in not exceeding 15mph in front of me on a 40 road with their left indicator going and no left turns for miles ahead. I got (believe it) 4 sets of 'V's' as I followed them and then again a lot more as I eventually was passing them. After passing and looking in my mirror They were still at thye four handed gestures so I put up the rear blind.
No other passengers in the car so who was doing the driving?
That old songline of 'old ladies, they have not only seen it but done it as well' appears to be very true. Courteous, innocent and pleasant old ladies those two were certainly not.