It was dark, in the early hours, and the sea was freezing as Her Majesty’s Submarine Conqueror came to periscope depth.
Her captain, Christopher Wreford-Brown, had been stalking his target methodically, a hunter in pursuit of wary prey.
Had they caught up through ingenuity, or by spying?
The issue was sensitive for the British, who had been plagued by spy scandals in the post-war period.
This was August, almost two months after the liberation of the Falklands, and on the other side of the world, in the Barents Sea, backyard of the mighty Soviet Northern Fleet.
Conqueror was sailing as close to Russian territorial waters as was legally allowed – or maybe closer.
Soviet submarines were not just becoming quieter and faster, they were able to turn the tables on their supposedly more advanced Western opponents.
“When we think of the Cold War we think of Cuba and Berlin and missiles and tanks, but it was at sea, and under the sea in particular, where the East-West struggle was often at its most dangerous.
Their final position was that, although they wouldn’t help, they wouldn’t try to stop me writing about it.” Throughout the 1950s and 1960s the Anglo-Americans rested on their laurels, confident of their superiority in naval technology over the fledgling Soviet fleet.
But as the 1970s wore on that confidence was eroded.
Submariners, a tight-knit community, politely disdainful of their surface counterparts, joke that there are two types of naval vessel: submarines and targets.
Wreford-Brown’s target was a spy trawler – an AGI in Nato parlance, meaning Auxiliary General Intelligence.