Ukraine invasion: Would Putin press the nuclear button?

Let me begin with an admission. So many times, I've thought: "Putin would never do this." Then he goes and does it.

"He'd never annex Crimea, surely?" He did.

"He'd never start a war in the Donbas." He did.

"He'd never launch a full-scale invasion of Ukraine." He has.

I've concluded that the phrase "would never do" doesn't apply to Vladimir Putin.

And that raises an uncomfortable question:

"He'd never press the nuclear button first. Would he?"