Far-flung dots on the chart, the Flannan isles are four hours north of St Kilda and twenty miles west of Lewis. The tiny archipelago is known as the seven hunters in Gaelic, Na h-Eileanan Flannach. When the lighthouse was automated in 1971, the last permanent residents abandoned its remote shores to sheep, seabirds and rabbits. And the phantom, of course – the islands are said to be haunted.
En route to North Rona, we stopped for one surprising and spectacular dive. We dropped from the rib into a gully so clear it was like diving in tap water. Marine life was vibrant, healthy, varied, and densely packed on every surface. The water surged and swelled, which made for tough filming conditions, but gave us wonderful images filled with colour, life and movement. Here are 45 seconds of Flannan highlights.