Contestants in the television quiz show Mastermind attempt to answer correctly as many questions as possible in two minutes on: (1) A specialized subject of their own choosing and (2) general knowledge. In this study, past contestants were asked to provide details of their performance in the competition. It was predicted that younger contestants would outperform older contestants under the speeded conditions of Mastermind because of their superior fluid intelligence. The main results were as follows: (1) Higher scores and lower tip-of-the-tongue (TOT) rates were achieved in the specialized subject round than in the general knowledge round. (2) TOT rate was positively related across the two rounds. (3) There was no effect of age on performance in the specialized subject round. In the general knowledge round, age was positively correlated with both score and accuracy. Thus, contrary to predictions, the older contestants actually outperformed the younger contestants (at least in the general knowledge round), presumably because of their superior crystallized intelligence. The results are discussed in terms of ‘limited impact’ theories of ageing, such that age-related decline in fluid intelligence does not necessarily occur for (a) everybody or (b) everything.