The National:

DAVID Mundell is a big fan of the Union? Who knew.

The Scottish Secretary isn't one who likes to keep to his cards close to his chest on the issue – but we didn't quite expect this public display of affection (PDA) for Westminster rule.

Every person has a tipping point though, and Mundell was pushed over his by SNP MP Patrick Grady during Scottish questions in the Commons.

He accused Mundell of "presiding over a power grab" during Scottish Questions in the Commons, adding: "Scottish Tories... have never wanted the Scottish Parliament to succeed and are using Brexit to undermine it."

Responding to the question, Mundell astutely observed: "He and his colleagues want to break up the United Kingdom.

“The integrity of the UK is a red line for me” when it comes to a deal with the EU, the Scottish Secretary added.

But perhaps unsure whether he had convinced ministers of his fondness for the Union, Mundell delivered the punchline: "I will defend our United Kingdom until my last breath.”

However, before the Tory had time to celebrate his, dare we say it, Mel Gibson-esque delivery, he was again under attack.

Shadow Scottish secretary Lesley Laird had the temerity to call his commitment to the Union into question.

She said: "The Secretary of State claims that protecting the integrity of the UK is the most important thing to him. The invisible man in the Cabinet even got a few headlines for himself this week by flip-flopping over his threat to resign.

"Sources close to him claimed he would resign but he denied it himself yesterday, so let's be clear – yes or no? If there is a deal that creates a border in the Irish Sea and undermines the Union, will the Secretary of State resign?"

Mundell insisted “it is not acceptable to me or my Scottish Conservative colleagues”, but the Labour minister showed that not everyone is convinced by the Tory’s Unionist credentials.

It matters not if this Union is going to drag Scotland into a disastrous Brexit – Mundell will fight to the last for it.