Electricians were shocked to find an unexploded World War II bomb at a former home of a war veteran.
The workers were rewiring a loft in Balsall Common, near Coventry, on Tuesday when they found a suspected German pipe bomb, police said.
West Midland Police secured the scene and called bomb disposal experts.
"They x-rayed the cylindrical shell, which was about 10 inches (25cm) and confirmed it was a live incendiary device," a spokesman said.
The device was found packed inside a secure, explosive-resistant box, police said.
'War veteran's home'
Officers escorted the bomb to a nearby field where a controlled explosion was carried out shortly after 1400 GMT.
Sgt Tony Hanlon said: "One of our Pcs is a former Army man so he went into the loft to look over the find… he suspected it was an explosive of some sort.
"We believe a former war veteran used to live in the house so may have been holding on to it as some sort of keepsake.
"However, as mementoes go, it was a pretty hazardous one!"
A low-fly exclusion zone was imposed over Balsall Common while the explosion was carried out.
As the device was found in a large detached house, officers said it was not necessary to evacuate other households nearby.