Wait until it dies back in the autumn. Perennials are usually best moved when dormant.

Yes, normally I'd agree, Stera, but the soil is warm and I reckon Noblegr could get away with it.

Many thanks Steragram and Spritzhenry. I am not particularly in a hurry to move it. I think I will wait until it dies down then.
Miriam

Have to confess I've been moving things but didn't want to be responsible for anybody else killing theirs off!