With grateful thanks to my three sons:

Tim, who found references for me and dedicatedly read each draft through for errors of meaning at which he then laughed immoderately;

Sam, who generously let me write about him and also kept up a supply of comic relief for his serious mother;

and Rafael, who arrived just as I was embarking on the bulk of the research for this book and who happily snuggled and breastfed while I read and wrote in the very early hours of the morning.