A study was conducted into the mathematical needs of engineering apprentices, triggered by a decline in the basic number skills of applicants. The mathematical challenges of engineering differ from the mathematics taught in school. In particular, great precision is required and different techniques; a good deal of practical problem solving is necessary, too. Conventional measures of educational attainment had high predictive validity; a test created to sample the mathematical skills directly involved in engineering had low predictive validity. We conclude that perfect mathematical technique is essential in engineering; the competencies learned from a broad-based education generalise to practical work; acquisition of mathematical technique does not; technical perfection is not a 'foundation', but rather is a component of mathematical education; mathematics education should encourage the development of a broad range of skills and some successful application of technique; and the deployment of skills in a range of contexts should be encouraged.