I believe these are called "Marinov motors" and not surprisingly work on the Marinov principle.
From memory, the original article written up in E & WW was published on April 1 which led many at the time to assume it was an April fool day prank, which it most definitely was not.
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Oh goodness, you must be nearly as ancient as me Brian.
Yes, I remember those verbal jousts between Ivor and his nemesis clearly, even after all these years.
Classic good fun !