Ask someone if they have ever killed a philosopher and the answer will probably be "no". But ask the ghost of one 17th-century monarch and she may reply: "Well, maybe, and I'm really sorry for being such a fool."
Queen Christina of Sweden was into self-improvement. Known as the Athene of the North, this would-be wise owl paid scholars from all over Europe to come to teach her in Stockholm. She wanted her city to rival London and Paris as a centre of learning, and one man in particular was crucial to the realisation of that dream. His name was Rene Descartes. He was France's top brain - a philosopher, scientist and mathematician.
In 1646, Christina started to write him letters. She asked him about the nature of love - not the normal sort, of course, but the sort that interested philosophers. Then she questioned his ideas about an infinite God and then she begged him to come to Sweden.
It was a long and difficult journey in those days and Descartes resisted her for three years. Finally, in 1649, he reluctantly agreed. Christina was 22 at the time. She was a mould-breaking intellectual who had already declared she would never marry. When she wasn't studying, she liked horse-riding and talking politics. She didn't like sleeping, regarding it as a waste of time.
Descartes, by contrast, was a rather frail 50-year-old who liked to stay in bed until 11am. As the man who came up with "I think therefore I am" he was entitled to long meditations. However, when he got to Stockholm he had to change his ways. Christina demanded that lessons start at 5am and continue for five hours. Descartes, who was staying with his friend the French ambassador, had to get up and walk to her palace in what was the coldest cold-snap for 60 years. He commented that men's thoughts froze like water in a Swedish winter.
When the French ambassador caught pneumonia, Descartes nursed him back to health, but alas, he was not so lucky. Weakened by his punishing schedule he died from the same disease on February 11, 1650, just months after succumbing to the wishes of the Athene of the North and moving to Stockholm.