raving mad

He looked at me as if I was stark raving mad.

"But I think the Conservative Party would look absolutely stark, raving mad if it had another PM. I think it would just entrench the brand problems that are all there."

“The investors of the Virginia Company were raving mad when they chose the men for this journey.”

Putin looks — how to put this nicely? — completely bonkers, or what the British call “starkers,” short for stark raving mad.

He is mad, stark, raving mad, and it’s no use my trying to stop him.