Pensioner used live artillery shell as a doorstop for 20 years

The First World War relic also served as a toy and finally, for the past 20 years, as a front doorstop at the home of 68-year-old Thelma Bonnett.

At any time during all those years, however, it could have exploded.

The German squat shell was live, packed with its original payload and with its firing mechanism primed, experts have said.

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It was only when a neighbour saw the shell outside Mrs Bonnett's door that the danger became clear.

The police were called and they summoned Royal Navy bomb disposal experts to the house in Paignton, Devon.

Several neighbours were evacuated from their homes and the device was taken to a local quarry and exploded.

It had been in the family for nearly a century after her grandfather Arthur Croxall brought it home in 1918. "I had no idea it was dangerous," Mrs Bonnett said.

"Grandfather picked it up on his travels with the Merchant Navy in

1918. My father used to polish it all the time and kept it on the mantelpiece.

"It looked German because of the writing on the top.

"When I was young, five of us children would play with it. I don't think he would have brought it back if he'd known it was live."

The mortar shell was seen propping open the door by neighbour John Malinovskis.

He said: "I put two and two together and thought, 'That really shouldn't be there'.

"I asked Thelma if she knew about it and she said, 'Oh yes, it's from the war'. She said her father had polished it and kept it on the sideboard."

Mrs Bonnett's son Steve added: "I remember it in my grandparents' house when I was growing up. I probably played with it a few times. It was just one of those things that was always around."

A spokesman for the bomb squad said a firing mechanism had been activated during the First World War but the shell failed to go off. The mechanism had since fallen off but the 'live' charge could have exploded at any time.

Mortar shells are fired at a steep angle with a plunging trajectory so they either explode in the air above the enemy positions or upon impact.

Light and portable, mortars were an effective weapon on the Western Front where soldiers faced one another in well-defended trenches.

A Ministry of Defence spokesman said: "The shell was packed full of explosives and it could have gone off at any time.

"It was brought back from France in 1914 and had been used in battle when it had been fired but failed to go off.

"There is a time delay on these type of shells. A brass ring could be turned on top which gave them enough time to fire it to go off in the air or on the ground."