Trying to remember a book title

[CanadianJohn]

Maybe someone could help me with finding a book I read a few years ago ... I can remember neither the title nor the author.

Young adult story - the protagonist is a 15 year old boy

Set in England, pre-internet, pre-cell phones, so maybe 70's or 80's.

Post-apocalyptic - the apocalypse is that everyone in the world ages very rapidly, and dies - except for our protagonist

The boy is an orphan, lives in a small town with his grandparents at the start of the story.

After the apocalypse, he moves to London, meets a couple of girls

I can remember a VERY few additional details, but maybe this is enough to identify the book

This book affected me greatly - if I'd read it as a teenager it would have really disturbed me.

Any thoughts?

Empty World by John Christopher, I thinkk

I did read it as a teenager, I was a fan of “almost everybody dies” apocalypse books - Day of the Triffids, The Kraken Wakes, Children of the Dust. The main thing I remember from Empty World is one of the characters stealing pictures from the National Gallery or jewels from the Tower of London or similar, - or maybe they moved into the National Gallery - when I go to the National Gallery now I’m always playing “which pictures will I have in my living room post apocalypse.”

Yup that's it. The local library has it "in storage", so that's my weekend reading taken care of.

Thanks.