Unfortunately it is practically impossible to say where and when the bottle entered the sea. In addition to pure tidal streams, there will also have been weather effects (i.e. wind) acting upon the bottle at any given time which may have resulted in it moving in an unpredictable way.

So the tides retained their secret. The bottle could still have come from almost anywhere along the northern French or Belgian coast, or been thrown from a boat.

When I was trying to find out more about the history of letters in bottles, and objects drifting around the seas, one name kept cropping up. I had first heard about Curtis Ebbesmeyer, a Seattle-based oceanographer, when a flush of rubber ducks began to wash up around the world’s beaches, attracting media interest. In January 1992 a North Pacific storm dislodged 29,000 bath toys from their container on an ocean-going freighter – and the Rubber Duck Flotilla was launched. Since 1966 Dr Ebbesmeyer has been mapping sea currents. At first he used to drop buoys and markers and follow their progress, but then he realized he could use existing shipping debris. Now Ebbesmeyer is ‘the big Kahuna’ of beachcombers. He tracks the cargo that manages to make its escape from the 100 million or so containers that are shipped around the world each year. Apparently, 10,000 of these containers – each 8 by 40ft, containing, say, 10,000 trainers – fall overboard and their contents are dispersed across the seven seas. Ebbesmeyer’s calculations are surprisingly sophisticated. He factors in wind resistance: shoes, for example, tend to float upside down, offering zero wind profile, while rubber ducks’ heads catch the breeze. So a duck takes about three years to go round the North Pacific, whereas a trainer takes six. In the millennium year 2000 a million pieces of Lego were lost from three containers in the Atlantic and are expected to make their way to land via the Arctic and the North-East Passage. Ebbesmeyer expects some of them to arrive on Alaskan beaches in 2012 and on Washington beaches in 2020.

Apparently he has never found a letter in a bottle.

Beaches have their own specialities and, in an article for National Geographic, Ebbesmeyer explained, ‘They’re like restaurants – some serve Thai food, some Indian or Chinese food. Some beaches are known for their glass or driftwood or artefacts.’ Some serve sea beans, seeds that have fallen from trees and plants that grow on shores around the world, mainly in tropical climes, and there is a whole sea bean subculture that collects them, identifies them, polishes them and writes about them.

Dr Ebbesmeyer runs Beachcombers’ Alert, ‘a place on the web where beachcombers from around the world obtain and exchange information’. I decided to ask his advice about the bottle. I sent him all the details I had about where the letter had been found. He answered my email with unnerving swiftness a few seconds later:

Dear Karen,

Thanks for providing as much information as you can.