Q What’s this lovely summerflowering plant?

A Romneya is a hardy herbaceous perennial with blue-grey leaves and these enormous white poppy flowers. Native to California, it needs a well-drained soil and full sun. It’s available in this country, but can be slow to establish. Ironically, once the plant settles down, its roots can be very searching and can get into paths and brickwork and can be difficult to control.