Mark Rylance has dubbed himself the Prince of Wales's "crop circle counsellor" after revealing their shared interest in the phenomena.
While Charles is well-known for talking to plants, his interest in crop circles - flattened patterns in fields which some claim have an extra-terrestrial origin - has been outed by the Wolf Hall actor.
Mark said the pair remained in correspondence after Charles came to see him take on the role of Henry V at London's Globe Theatre in 1997.
He told Australia's Sydney Morning Herald: "We had a wonderful meeting and then he came to the Globe several times.
"I still call him 'sir' in respect for his extraordinary fate. He's just a human soul like you or I, but he's been born into this incredible fate and so I respect him as I would respect anyone who has had an extraordinary fate given to them."
He added: "And we correspond. He's interested in crop circles too, so I send him my crop circle calendars and magazines that I buy and keep him informed. I'm his crop circle counsellor."
Mark has most recently voiced the eponymous giant in Steven Spielberg's remake of Roald Dahl's The BFG.