I disagree. If he's lucky the clutch will eventually let go outside his house; if he's not, it will disntegrate whilst he's a distance from home - not pleasant for anyone but certainly not fair if, as you say, he's elderly. A discreet note, anonymous if you prefer, suggesting that he has his clutch checked would be in the interests of common civility.

There is a good chance that the clutch is not on its last legs but, The driver is slipping the clutch.

I have observed this a few times with elderly drivers, That they get to a stage where they give the car alot of revs and then slip the clutch to control the speed. Obviously it is not good news for the life of the clutch.

Some older people do drive like this for some reason, it's probably better than trying to master some horrid automated manual after 50 years with a clutch, and we tend to forget that older drivers will have been brought up on engines that didn't stall at the drop of a hat and you could easily get up to about 3rd gear and 20 mph on a trailing throttle on some.

However, i can still hear the sound of the huge electric drill screaming in protest echoing round Padstow circa 1972, it turned out to be a little old lady parking an Austin A35, never before or since have i heard a car engine reach such astonishing revs short of at a trackside.