It has described the Inner Sound, which lies between the Caithness coast and island of Stroma, as one of the Firth's "most energetic" tidal areas.

BBC: Pentland Firth tidal project set for development

Soon after, her cargo of slot machines, spark plugs, clothing, tobacco, watches and car parts was silently removed and hidden in the haystacks, oatfields, lochs and caves of Stroma until the customs men and coastguards had cleared off.

ECONOMIST: Shipwrecks and wreckers