I think they also have to be a real person (the site where I heard about this said so, but it isn't mentioned on the nomination page) rather than a fictional character, and British though they don't actually say so - I think any non-Brits will be fairly low on the list. They also ask for a very brief summary of the reasons why the person is important.
I've gone with Rosalind Franklin, one of the pioneers of X-Ray crystallography and an important figure in the discovery of the structure of DNA.
You can nominate on this page:
The page doesn't ask for any personal details about the person making the nomination.
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