Thankfully, however, there were some Gallifreyans who had the foresight to stay home and build a future for their planet.

These included people like the solar engineers who, having discovered that the square root of minus three was impossible to calculate, had their biological engineers develop a new species of animal which had that knowledge bred into it. Thus, when any planet on which this animal was placed tried to find the square root of minus three, the animal would turn round and say “Ah, but that’s impossible”.