PPC fine from 2013 went quiet after appeal, now a debt collect letter out of the blue years later

Coupon-mad

I negotiated to settle for a sum equivalent to the PCN charge and the claimant's initial court fee, a considerable discount against what was demanded.

OK, at least you didn't pay the sum they were demanding.

the case would then move on to the merits of the original PCN, which I had no compelling argument to contest.

You did - PPS' signs at the time were illegible an only the word 'WARNING' was in large letters. And there was no chance in law that they could hold a registered keeper liable, at all, in 2013, as PPS were not using POFA-compliant PCNs.

Not replying to your appeal was never a defence point anyway, so them showing evidence of that changed nothing abut your case, which 99% of people here, win.

You'd have had a very, very good chance of beating them.

I think that simply "keeping quiet" does not provide adequate cover if you are later taken to court. And remember to keep good records of any such communication for the full 6 years...

Good advice, and you didn't ignore it in 2013 so you played it right at the time. And it was PPS that went quiet for several years, which you could have used against them.

Shame you settled really, but thanks very much for coming back!