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The rule that the current activity takes priority over another pending activity, derived from the BBC quiz show Mastermind's catchphrase "I've started so I'll finish." The rule can be invoked at any point during the activity, but is not necessary should the alternative be more favourable.
Jon Humphreys: What is the capital *beep* - I've started so I'll finish - of Namibia?
Contestant: Windhoek

Miles: Can you pass me the kingers so I don't have to map out, actually I''ll invoke the mastermind rule as I've started so I'll finish.
by Burger King Diamond August 15, 2011