I would particularly like to thank Rodie and Tony Sudbery for their very helpful ideas and comments on large parts of the text. I am also very grateful to Neil Turok, Eleni Haritou-Monioudis, John Szymanski, Jeremy Jones and David Olive for detailed comments on particular sections, and my father, William Tutton, for his helpful advice on my drawings. I would also like to thank the mathematics department of the University of Wales, Swansea, for helpful discussions concerning the needs of incoming students. The referees also all provided detailed and useful input which was very helpful in structuring the book and I thank them for this.
I would also like to thank Rufus Neal, Harriet Millward and Mairi Sutherland for their patient and friendly editorial help and advice, Phil Treble for his great design, and everyone else at Cambridge University Press who has worked on this book.
Finally, I am particularly grateful to my daughter, Rosalind Olive, both for her helpful comments and also for her excellent guinea-pig drawings.