Oliver's Island derives its name from a story that Oliver Cromwell once took refuge on it, but there is almost certainly no truth to this. It was called Strand Ait until a century after the Civil War, by which time a myth had arisen that Cromwell had set up an intermittent headquarters at the Bull's Head, Strand on the Green. The story was embellished with the suggestion that a secret tunnel connected the island to the pub, but no evidence of any tunnel has ever been found.
In 1777 the City of London's navigation committee installed a tollbooth on the islet to levy charges on passing craft to fund improvements to the river’s navigability. This was a wooden structure in the shape of a small castle, and a barge was moored alongside, from which the tolls were taken. This "City Barge" gave its name to the pub at Strand on the Green. A smithy was on the island by 1865 and it became a place where barges were built and repaired. The smithy was only demolished in 1990.
The cache is not at the listed coordinates, which is lucky because I don't have a boat and I don't fancy the swim. It is nearby though, with a lovely view of Oliver's Island. Even though the connection to Cromwell is dubious, the name has stuck for centuries and so here is a puzzle in his honour, made up of words associated with his controversial history.
