Are you sure it is a tree peony and not an intersectional? There are literally 1000's of cultivars and many without names so narrowing it down to a single one is going to be difficult at best.

I have no idea. How do I tell if it's an intersectional? It forms a a permanent woody framework and flowers on new shoots growing from last year's branches. It's almost certainly something very common. I got from a neighbour who was not much of a gardener.

If it has a permanent woody framework, then not an intersectional. They have tree peony flowers emerging from an herbaceous base :-)

In the past, all tree peonies originated from China and a brief online glance at a photo catalog shows multiple cultivars that look very similar to yours. Do you have a UK peony society you could send photos to for a closer ID?

Unnamed seedling may perhaps also be possible.

It could be Hana Kisoi

That looks like a possible candidate. Thanks.

floral_uk z.8/9 SW UK

It looks like 'Hana Kisoi'!

Um, yes...