The BA training place at Cranebank had a Cabinet of horrors, including a pice of work with a drill stuck in it, and about two feet of hair. That dated from early Seventies. My luckest cock up was being to lazy to put proper axle stands under the back axle of a LWB Land Rover. I then yanked hard at a nut with a torque wrench. Fortunatley I put so much force on the bar I tipped my head back, as the wagon slipped off the jack. I was luck enough just to get a side swipe. The most jaw dropping stupidity I've ever seen was a 'visiting mechanic'. He had parked a vehicle , on a slope, with two wheels on the pavement. Then jacked up the road side , with a single trolley jack, and gone under it!!! Not even a wedge under a wheel!
Poinr of Order: Manufacture of cannon started at Woolwich following an acident during casting at White Chapel. At the time bell foundrys were the ones with the expertise. I'm sure Alan can find the details, but a brass cannon was being forged and the sand was damp! The resulting explosion killed several notables including the King's Master of Ordnance at the time.