The Irish lighthouse that gave D-Day the green light

Eisenhower and his commanders faced a real dilemma balancing secrecy and success.

Launch the invasion in bad weather and risk failure, or delay and increase the chance of the invasion plans leaking.

British Prime Minister Winston Churchill had already imposed a ban on travel and communication between Britain and Ireland, both north and south, on 14 March 1944.

But weather reports were still being received from neutral Ireland under an agreement signed between the two governments in May 1939.

Information from 10 Irish weather stations – including Blacksod – was supplied hourly. And on 4 June the crucial information came through.

Group Captain Stagg believed a ridge of high pressure was building up from the Azores.

A ridge that would give a window of better weather.

And on 4 June, confirmation came from Belmullet when Ted Sweeney reported: “Heavy rain and drizzle cleared, cloud at 900 feet and visibility on land and sea very clear.”

At 04:15 on the morning of 5 June 1944, Eisenhower met with his senior staff and told them: “OK, We’ll go.”