“I like the fact there was so much available, not just in his writing but in the writing of contemporaries, and particular descriptions of him – what his voice sounded like, how he spoke, how he was generous with his ideas, his sense of humour was very wry. He was a very witty kind of person.

“If confronted he could be very cutting and somewhat arrogant, but so could Jung be - they were very proud, and in some way insecure, which makes for interesting drama. All of a sudden these are people like us, they’re not just these great historical personages, these scientists, these thinkers. It made them more human, more like you and me.

“They could make jokes, they could be competitive, they could be ambitious, they could be jealous - they could be very affectionate in their way as well. All those things made it a lot more interesting to play.”