For a book of its genre, our previous book, An introduction to gauge theories and the “new physics” (1982) was a great success. It was not, alas, sold in airport lounges, but it did run to two additional printings (1983, 1985), and to extensively revised editions in Russian (1990), and in Polish (1991). More importantly, it seemed to achieve the principal goal which we had set ourselves, namely, to present a pedagogical account of modern particle physics with a balance of theory and experiment, which would be intelligible and stimulating for both theoretical and experimental graduate students. We did not try to write a profound book on field theory, nor a treatise on sophisticated experimental techniques. But we did wish to stress the deep, intimate and fruitful interaction between theoretical ideas and experimental results. Indeed, for us, it is just this aspect of physics which makes it seem so much more exciting than say pure mathematics. Our greatest pleasure came from the favourable reaction of students who were working through the book and from those reviewers who caught what we hoped was its essential flavour—‘the writing creates the feeling of an active progression of ideas arising from the repeated interaction of theoretical prejudice with experimental observation’, ‘unlike most textbooks, it is highly readable, and makes everything appear simple and obvious’. Well, the last comment is surely an exaggeration but that was our aim.

In thinking about a second edition we were faced with a serious conceptual problem. Ten years ago we were in a state of excited expectation.