Have you been to Halfords lately? In the run-up to Christmas the place has become a Santa's Grotto of desirable stuff, from sat-navs and car stereos to bikes and games tables, mostly aimed at the male of the species. But the company's slogan, 'We go the extra mile', is about service rather than products, and it powers a series of television ads in which helpful silhouettes cheerfully fit those stereos, show how to use those sat-navs, and safety-check children's bikes. The target seems to be the female consumer, for whom car-parts stores have been an alien place. The slogan, created internally, is ingenious, incorporating a saying that some say has its source in Jesus's Sermon on the Mount: 'And whosoever shall compel thee to go a mile, go with him twain.' To go the extra mile is to do more than is required of you. But the use of the word 'mile' is a bonus, reminding consumers of Halfords' roots as a store for motorists. The slogan and TV ads make a bold promise. There's nothing wrong with that. The problem is keeping it.