I like your thinking, quisling, (which incidently is the solution, I think, to another of the questions/clues). Your suggested answer fits with the style of others and my wife had thought of Gabriel Oak but sadly I didn't make the connection to quercus/quercia.
The quiz is to raise money for a choir and has been set on an annual basis for many years by the husband of one of the singers. Each quiz has had a separate theme but this is his last and we've never won so this is our last chance.
There's a small cash prize which we'll donate to the choir should lady luck smile upon us.
Thanks again for your suggestion.