It happened on the evening of September 25-26, 1916, when Zeppelin L14 had Leeds in its sights.

The airship was looking for the industrial targets of Barnbow and Kirkstall Forge but it aborted its mission when it came under fire and ditched its incendiary bombs.

Thirteen of them landed in soft mud on the Harewood Estate and failed to go off. They were later defused by experts and one of them was displayed in the Harewood Arms pub.

Five of the bombs are now in storage at Harewood but one of them is on display in the house itself.

The fascinating story behind the Harewood raid has been researched and told by Andrew Stokell, collection management and stores officer at the University of Leeds.

He has self-published Target Leeds: The Attack By Zeppelin L14 and hopes to sell it to military enthusiasts.

"I blame my father Rex for starting my obsession with Zeppelins, " said Andrew, 39, of Sherburn-in-Elmet.

"He was six-years-old when he saw a craft in the sky which was not an aeroplane.

"We think it was the Hindenburg airship on its way to New York. That memory fired my interest.

"My father also told me that he had seen a TV documentary about a bomb being found in the attic of Harewood House and the story of how it came to be there was one I wanted to research."

Andrew contacted the National Archive in Washington DC for details of the raid from seized German naval records which are held by the Americans.

And he got much information from German archives, particularly the Zeppelin Museum at Friedrichshafen on Lake Constance.

Andrew said that L14 crossed the East Coast just north of Hornsea and reached York by 12.15am on September 26.

The crew dropped bombs and then intended to target Leeds but their mission went astray.

Navigation was always a problem anyway and the crew of L14 suddenly came under fire from a lorry-mounted gun as they passed over Collingham or East Keswick.

Andrew said: "The gun fired nine rounds and then jammed which was lucky for the Germans as they were directly overhead.

“They appear to have decided that their mission was up and they dropped their bombs over Harewood estate.

"In the early years of the war they literally dropped them by hand but later they had a bombing machine which lined the weapons up a bit like a wine rack and dropped them electronically."

Andrew managed to obtain copies of pages from L14's war diary which included its navigation map over the North Sea and back to its coastal base.

Zeppelins were the first terror weapon and initially came over unopposed. They could climb higher than the early RAF fighter planes.