HL Mencken used to say that nobody ever went broke underestimating the taste of the public, and Channel 5's first half-decade seems to have confirmed that. The channel has cornered five per cent of the TV audience, and on good nights recently has been doing considerably better. The 3F formula ("football, films and f***ing") appeared to be working. Why, then, are Channel 5 executives now earnestly declaring that they want to put the past behind them and raise the quality of the output, especially when advertisers are telling them that they like the male audiences pulled in by the porn?