I am firm. You are obstinate. He is a pig-headed fool.

Bertrand Russell (1872-1970) English mathematician and philosopher

Comment, Brains Trust (BBC Radio) (26 Apr 1948)

Offered as an example of conjugating an irregular verb. Quoted in "Result of Competition No. 952" The New Statesman and Nation (15 May 1948). (Reference) Sometimes attrib. to British journalist Katharine Whitehorn.