Ah, this I think may have been the Grenade, hand or projector, No. 76, otherwise known as the 'SIP' or 'Self-Igniting Phosphorus' grenade.
Designed by Allbright & Wilson of Oldbury, original trials for the RAF on July 29th 1940 consisted of the very simple method of glass bottles filled with the phosphorus mixture being thrown at pieces of wood and into an empty hut.
The results were quite encouraging but not to the RAF , who commented that 'carriage of spontaneously inflammable liquids in aircraft is not considered to be desirable'.
The No 76 was introduced in 1940 and mainly issued to Home Guard units before being declared obsolete in February 1944. The Home Guard apparently buried lots of these or hid them in the attic ; if you find one, don't throw it in the living room....
