JK Rowling may actively answer hundreds of questions daily on Twitter about the Harry Potter series, but there are still some secrets left unknown.

Thanks to the BBC’s new documentary, Harry Potter: A History of Magic, celebrating the 20th anniversary of Harry Potter and the Philosopher’s Stone, a few more tidbits of information have been revealed.

Rowling herself appeared on the programme, discussing the origins of the series. One notable moment came as the author spoke about sketching the character Professor Sprout.

While drawing an initial version of the herbology teacher late one evening, Rowling was watching The Man Who Would Be King, John Huston’s adaptation of Rudyard Kipling’s work, starring Michael Caine, Sean Connery, and Christopher Plummer. The next day, Rowling took a phone call saying her mother had died.

“The Masonic symbol is very important in that movie,” said Rowling. “And it was literally 20 years later that I looked at the sign of the Deathly Hallows and realised how similar they were.

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“When I saw the movie again and saw the Masonic symbol, I went cold all over and I thought, ‘Is that why the Hallows symbol is what it is?’

“And I’ve got a feeling that, on some deep, subconscious level, they are connected. So I feel as though I worked my way back over 20 years to that night, because the Potter series is hugely about loss, and – I’ve said this before – if my mother hadn’t died I think the stories would be utterly different and not what they are.”

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