The cover story for all the activity around the strange island of Memmert is readily given by Von Brüning: they’re after a wreck.
‘I don’t wonder you heard of it. It’s one of the few things folk have to talk about in these parts. It lies on Juister Riff, a shoal off Juist. She was a French frigate, the Corinne, bound from Hamburg to Havre in 1811, when Napoleon held Hamburg as tight as Paris. She carried a million and a half in gold bars, and was insured in Hamburg; foundered in four fathoms, broke up, and there lies the treasure.’
We wondered if the Corinne was a real ship, and so I spent some pleasant hours scouring an amazing site called wrecksite.eu, which is a sort of Wikipedia of maritime destruction. It revealed that, sure enough, these Frisian sands, west and east, are littered with wrecks. Here’s a snapshot of the mouth of the Ems which gives a good idea of the chaos on the seabed:
However, there was no trace of the Corinne down there, and we could find no French vessels with that name. However, another possibility presented itself as the possible model for Childers’s sunken treasure ship. Anyone familiar with Lloyd’s of London, the insurance underwriting exchange, may also be familiar with this chap, or more specifically the thing he is ringing:

That is the Lutine Bell, in the Underwriting Room. Traditionally, it was rung to announce the fate of a ship which had been late at its destination port. If the ship had arrived safely, the bell was rung twice; if it was sunk, it was rung once, to immediately stop the sale of any further reinsurance on the downed vessel by unscrupulous insiders. These days, the two rings mean there is a distinguished visitor to Lloyd’s. One ring is used to note events or anniversaries, such as Remembrance Day.
The Lutine Bell is all that remains of HMS Lutine, a fighting ship of the Revolutionary Wars which was launched by the French Navy in 1779. She was a Magicienne-class vessel with 32 guns, a frigate, and in 1793 she was handed over to a British naval fleet when the French port of Toulon was seized by royalists and, effectively, handed to the British. She kept her name, with a new prefix: HMS.

She served her time in the North Sea, participating (among other things) in a blockade of Amsterdam. In October 1799 she was sailing from Yarmouth to Cuxhaven (the same Cuxhaven Carruthers and Davies sail past in the Dulcibella). She was carrying £1.2 million in bullion and coin which, it seems, was to be used either to prop up the banks in Hamburg or to pay for Anglo-Russian troops that were then making their way into North Holland.
She never made it. Drawn by the tidal stream flowing into the Waddenzee – the Dutch word for the body of water at the mouth of the Ems – she hit a sandbank off the island of Terschelling, in the West Frisians, and she went down. All 240 souls aboard were lost.
What happened next was an exercise in salvage and sophisticated reclamation of assets – or, if you like, wrecking – which still attracts scholars to this day. As soon as the vessel hit the seabed, the bed began to eat her up, as sand piled up around her, and for the coming decades that remained the pattern – the ship being revealed and reburied, revealed and reburied as the sands moved around her.
This made salvage difficult, as did the ongoing dispute between Lloyd’s and King William I of the Netherlands over who actually owned the wreck. The gold on the Lutine had been insured by Lloyd’s, who had paid out their policy in full (insurance was an easier matter in those days) and thus owned the gold under international maritime rights of abandonment. The Dutch, however, claimed the ship as a prize of war. A complicated arrangement was made to share the gold between the Dutch salvagers and Lloyd’s, and so valuable was the potential that this was enshrined in the Lloyd’s Act more than 70 years after the sinking.
Wikipedia lists more than 20 separate attempts to raise the gold, but it’s estimated 80 per cent of the stuff is still down there. So famous was the case of the Lutine that it seems entirely feasible that Childers based his own treasure ship, the Corinne, on the Lutine.
And given how much gold is still down there, we might take masks and snorkels with us. Or perhaps just metal detectors. You never know.