34 miles north-north-east of uninhabited St Kilda, itself 55 miles off South Harris, the remote discovery appears to confirm observations by ancient cartographers, who from 1325 onwards insisted on the existence of an outlying island explorers described as a ‘promised land’. The name derives from the celtic word Breasal meaning ‘High king of the world’.

Historical descriptions of the island – once thought shrouded in mist for all but one day every seven years – vary in spite of landings being made in 1480, 1481, 1497 and finally 1674 by Scottish captain John Nisbet, who sent a party of four ashore. In Nisbet’s account the sailors were met by an old man who told them he lived alone in a castle on the island. The remains of what appear to be a castle on Breasal Beag (an islet separated from the main island by a sandy sound), may corroborate the report.

The discovery has been hailed by the National Trust for Scotland, whose spokesman David Dennison said: “This is perhaps the most astounding gift ever made to the National Trust for Scotland. Our priority will be to send a survey party to record Hy-Breasal’s flora and fauna, especially the rumoured colony of Lepus ater."