Someone I know shouldn't be driving. In my opinion.

I know the feeling. I have heard that a relation by marriage is so unfit to drive now that he struggles to change gear, so I imagine his ability to brake is equally bad.
It only being heresy, and there being several much closer relatives, both by blood and geographically, who I would hope would take action if things are as dangerous as they sound, I am hesitant to do anything, and I would even have to go behind OHs back if I were to report my concerns.
However, I am very seriously considering doing that, as I would never forgive myself if he were to injure someone,or worse.

We were very concerned about my fil driving a few years ago . He was 94 then
My husband and mil weren't keen on talking to him about it , because he just dismisses you . Then he had an accident in a local shopping centre , totally his fault , he couldn't argue as they had it on cctv he was very lucky no-one was hurt, he never drove again

It's hard, as a) everyone's different (My Mum at 87 has really quick reflexes).
b) Cars give old people independence if their mobility means they can't walk far.

It is up to the people who know them best, to say something to them in most cases I think.If they DO have an accident (hopefully not, & low speed crashes are less dangerous) then blame's on those close to them, not you.

You can report anonylously to the DVLA and you definitely should.

I hear so much of people saying that the person only drives around the local area - children run out from behind cars even in the local area.

You can probably report him anonymously to the DVLA if you're concerned. I expect there is guidance on the gov.uk website.

We were relieved when my late dad decided not to drive after the age of 86. He used to think his car was faulty when he actually didn't have the strength to operate the pedals or gearstick properly. He hated losing his independence but he knew it was the right thing to do.

Please report them. No-one's independence is more important than someone else's life. Someone will go along and assess the situation, they may think they're fine.

The difficult comes from the fact that you don't know for sure, unless I've misunderstood? You are basing your concern on the fact that you are sure that reactions slow with age. IMO that is not enough to go on to deny someone the right to drive.

Of course, if you are sure that he personally has slow reactions and poor eyesight then it's a different matter, but just going on your post you are prejudiced against him because of his age.

Minding your own business is a harsh way of putting it, but just knowing that a driver is in his mid 90s doesn’t seem to me to justify reporting him to the DVLA. It smacks of vigilantism.

Anonymous reporting is a bit cowardly. If you feel strongly enough to take action, I think that action should be talking to the man himself, certainly in the first instance.

Three people i know were not fit to drive in their 80’s, in the end they all wrote cars off and couldn't get reinsured, just glad no one was hurt. One, my fil, wouldn't listen to us and got quite angry, he went on a motorway the wrong way and still blamed the other drivers when his car was written off.

Please report anonymously. If they appeal they can take a test.