SPAIN’S generals believed they could seize the Rock in just 20 minutes.

Meanwhile, Adolf Hitler’s troops predicted two or three days, at the start of the Second World War.

The claims are all part of a fascinating new book on Gibraltar, Defending the Rock – How Gibraltar defeated Hitler, by Nicholas Rankin.

Timed to come out just before the 50th anniversary of the Referendum vote, the book highlights Hitler’s regret at failing to take Gibraltar.

It also explains the territory’s strategic importance during the war and its history before it.

One of its main thrusts tackled its defences, with even the British highly concerned at how easy it would be to take the Rock.

Indeed, aide to the then governor, actor Anthony Quayle, thought the Garrison was ‘as impregnable as a poached egg.’

“The Spanish could have walked in with a troop of boy scouts,” he claimed.

However Franco feared that if he were to take the Rock, the British would retaliate by invading the Canary Islands.

It led to him remaining neutral until Germany had defeated Britain – something he expected to happen quickly.

This flew in the face of Hitler’s plans, which were to see an invasion launched on January 10 1941.

But he was somehow talked out of it during a long nine-hour meeting with Franco on the border with France.

Franco recognising Hitler’s vulnerability presented a long shopping list that included the annexation of Morocco and lots of wheat.

It was a step too far for Hitler, who later reflected that he would prefer to have had ‘three or four teeth taken out’ rather than to go through the meeting again with Franco.The plans were called off.

Hitler later hinted that his failure to take the Rock was his gravest mistake during the war.

Defending the Rock is released on September 7.