The 29mm Spigot Mortar or "Blacker Bombard" was invented by Lieutenant-Colonel Blacker in the early years of WW2 as a cheap and easily produced weapon to replace ordnance lost at Dunkirk. It was extremely heavy (around 350lbs).
The weapon fired a 20lb fin-stabilized anti-tank bomb warhead containing a high explosive charge. It had an effective range with the anti-tank bomb of around 100-150 yard. It also fired a 14 lb anti-personnel bomb with a maximum range of around 500 yards. They were fairly accurate and effective at short range. The weapon was rejected by the regular army but saw service with Home Guard and airfield protection units from 1941-1944.
This is a reprint of the official manual for the weapon, and covers the wepon itself, its ammunition, use and emplacement. With 4 A3 drawings of the weapon and bombs.