Recently I stumbled across a dusty old shop run by three old boys, with pullovers that were more holes than actual knitting & industrial sized tartan Thermos flasks, that specialized in valves, radio spares and ex-RAF equipment. I’d not seen a shop like this since Proops fizzled out at the end of the 80’s so I couldn’t resist a look, or walking out with a suitably photogenic box of gubbins.

Having researched a little it seems that Decca developed the Dectrac system initially as a maritime aid in the mid 1940s, but the benefits of having an onboard navigation computer were realized by the RAF for use, I suspect, in it’s longer range bomber aircraft such as the Canberra and the Vulcan. So, in the 60’s Decca took a very large MoD order for Mk.19 units such as this, which were successful enough to be manufactured into the early 80’s. Dectrac coverage was pretty much global, with a multitude of ‘Chains’ being set up across the ‘friendly’ World – not to be confused with the WWII ‘Chain Home’ early warning network. Chain 5B was for England, the earliest – being set up in 1946 and operating unitl 2000.

It is more than a little unsettling to think that in the event of M.A.D. – Mutually Assured Destruction – surviving RAF bomber crews were expected to consider England ‘hot’ [radioactive] and keep on going for somewhere remote such as the Pacific Islands, writing off their friends, families & country as dead. All out Nuclear War would in effect have reduced the entire Western Civilization to a few dozen aircrews stranded on islands and atolls living off survival rations and coconuts.