"We are a lot less powerful than we were during the Falklands and we are less sustainable over time. Our capacity for actually enforcing our national will in military terms is significantly less.

"Our war fighting assets are weak after years of operations in Afghanistan and Iraq and because of the disingenuous way in which the Government has resourced defence.

However, he insisted that Britain's military capability "significantly" over-matches Spain's and that if it came to a war, the UK is - qualitatively - three times more powerful. Our capacity to do them harm is far greater.

Bur he added: "We could cripple Spain in the medium term and I think the Americans would probably support us too. Spain should learn from history that it is never worth taking us on and that we could still singe the King of Spain’s beard”.