Odd but who knows...

The article goes on to acknowledge that the rumour is likely nonsense. Still I bookmark it here in case of prescience.
Prince Charles of Arabia - Middle East Quarterly - September 1997

Prince Charles has often surprised his future subjects, but few shocks match the allegations of a newspaper article that appeared in October 1996:2

The idea of the Prince of Wales lugging around a prayer mat and turning to face Mecca five times a day sounds a tad unlikely - but, then again, so did confessing to adultery on prime-time television a couple of years ago. So perhaps no one should be shocked by the suggestion in a forthcoming book that Prince Charles has converted to Islam.

This claim was put forward by no less a personage than the grand mufti of Cyprus: 'Did you know that Prince Charles has converted to Islam. Yes, yes. He is a Muslim. I can't say more. But it happened in Turkey. Oh, yes, he converted all right. When you get home check on how often he travels to Turkey. You'll find that your future king is a Muslim.'