Occidental Petroleum found oil at Piper in January 1973 and at Claymore eighteen months later. Both fields lay in the British sector of the central North Sea, far from any onshore terminal. Occidental considered offshore loading and pipelines to a number of mainland sites - nine in all - before choosing the small island of Flotta in the south of Scapa Flow. The choice was not obvious. Flotta is remote, with a population of fewer than a hundred, and laying a 130-mile subsea pipeline through the deep water and tidal currents of the northern North Sea was not cheap. But Scapa Flow offered something no rival site could match: a vast, sheltered anchorage where the largest tankers could load in almost any weather. The Royal Navy had used the same waters for the same reason in two world wars.

Phase 1 came online in 1977. The terminal was built around four stabiliser trains, each capable of processing 125,000 barrels of crude per day - removing dissolved gas and water so the oil could be stored stably and shipped by tanker. Peak production came barely a year after start-up: 421,590 barrels in a single day on 4 November 1978. Crude was loaded either at a jetty inside Scapa Flow or, in deeper water, at single point moorings further out. By the late 1980s, with Piper itself in decline and the Piper Alpha disaster in 1988 wiping out the original platform, additional fields were tied in to keep the pipeline full. Ivanhoe came in 1989, Galley in 1998 and again in 2007, Tweedsmuir and Duart in 2007, and the big one - Golden Eagle - in 2014, which effectively doubled the throughput.

By 2017, forty years after first oil, one of the four stabiliser trains had been quietly decommissioned. The remaining three had a combined capacity of 375,000 barrels per day - still substantial, but a far cry from the peak. The Single Point Moorings out in the flow were mothballed. The associated gas plant - originally built to extract and export liquefied petroleum gases - stopped making economic sense as gas volumes dwindled; today the gas is simply burned on site to generate electricity and heat the stabilisers. As currently operated, Flotta does only one thing: it takes in stabilised crude, stores it, and loads tankers at the jetty. In 2016 fifty tankers called. The terminal has outlived several of the fields that built it, several owners, and most of the original engineers.

The contrast between Flotta and the rest of Orkney is part of what makes the islands what they are. A few miles north sit the Neolithic stones of Stenness and Brodgar, five thousand years old. A few miles west lie the rusting remains of the German High Seas Fleet, scuttled at Gutter Sound in 1919. A few miles east, the Italian POWs who built the Churchill Barriers also built a chapel out of two Nissen huts and painted it like a Roman basilica. And here, between them, sits the flare stack and the tanker jetty, the late twentieth century laid over Norse, Pictish, and prehistoric layers without much apology. The terminal is currently operated by Repsol Sinopec. The flow that once held the British Grand Fleet now holds tankers waiting to load.