Yellow flower

We bought this little plant at an open garden event earlier this year.  The name tag was illegible - all that we could read was "yellow".  And the folks manning the stall couldn't remember the name, but assured us it had a pretty yellow flower.

We're suckers for variegated leaves, so we bought it.  It certainly does have a stunning bright yellow flower.  I've tried googling yellow flower with variegated leaves, but cannot find a name for it.

Cailleach will undoubtedly be able to identify it!