Following some links on another thread -
http://www.pprune.org/aviation-histo...-hounslow.html I found a fascinating site which may have the answer to the original query. It includes the entry:
Another Miles fixed wing plane is known to have slipped into Heston at dusk autumn 1956, this time without permission, the pilot had apparently lost his way. After a night in the hangars an aerial departure was allowed.
See:
http://www.commercemarketplace.com/h.../woodason.html