Filipendula rubra 'Venusta'

Hi floral

That is what I suspected, but was thrown by the huge basal leaves, and wondered if they were something else.

probably a volunteer in the bigger plant, leaves look very much like a Rodgersia

Yes, they do.

I'll keep an eye on it and see if a Rodgersia flower appears.

Thanks, guys

Just heard back from the head gardener who has confirmed that it's F. rubra 'Venusta' co-planted with Rodgersia.

Bang on, fig.

Thanks guys.