Ah! Happy memories!
Decca also ran other high precision radionav systems in addition to MainChain, such as Shoran, HiFix, Pulse/8 and Decca Trisponder.
In the early days of the North Sea there were really only two companies providing precise nav services for rigmoves and pipelay barges: Decca Survey and Kelvin Hughes. The nav guys were invariably referred to as "the Decca Man", even if they actually worked for Kelvin Hughes.
The General Manager of Decca Survey worldwide was neither a surveyor nor a navigator. He was the guy who, when he ran Decca Records, turned down The Beatles.
Nobody ever got fired from Decca, so they shunted the guy sideways into Decca Survey.
Decca Survey was later taken over by Racal, but for some years one of the Decca Survey companies retained its old name when all the others around the world had been subsumed into the Racal brand. That was the Bahrain company, Decca Survey Overseas Ltd (DSOL). It was known as Deezol. Racal spotted the obvious trap of changing DSOL into RSOL as Deezol would have become Arzole.
