In message , Ian Jackson
writes
Release. Balloon rises into the blue. Smouldering string reaches Jetex
fuze. Fuze ignites and fizzes. Balloon explodes with either a loud bang
(if the hydrogen contains a fair proportion of air), or a whoop (if it
is pure).

You'd probably get 20 years for doing that today!
You'd be lucky to get prison time, more likely to get shot in the head
by an armed copper.
--
Clint Sharp