Why Axis battleships in Dublin would provoke invasion

What if Ireland joined the Axis and based Italian battleships in Dublin?

Britain would almost certainly invade and destroy or seize the ships because the threat was strategically unacceptable.

Neutral sovereignty would not outweigh the strategic danger of Axis capital ships operating behind Britain's western approaches. Italian battleships based at Dublin could threaten Atlantic access at a moment when Britain's survival depended on imported supplies. The likely British response was an armored advance from Northern Ireland combined with Royal Navy and RAF attacks on the harbor. American political reaction would complicate the aftermath, but it would not make London accept an Axis fleet base so close to home waters.