Well, this should prove interesting. I got a reply from Ken & Jan Lardner who run the Chantey Cabin website.

"Cannot give you an immediate reply - but we are about to set off for the 2 biggest festivals of the year (Hull and Portsmouth) so we will find the definitive answer on our travels even if we have to call in the Navy (the Portsmouth Festival is in the Naval Dockyard)."

When I hear back from the Lardners I'll post the results to this thread.

Richard