Collingham is a well-known historian, and author of the fascinating Imperial Bodies: The physical experience of the Raj. In Curry, her tone is less overtly academic but this book, too, is based on exhaustive research and full of intriguing nuggets of information. It will be welcomed by scholars of food history, and curry enthusiasts should find it riveting, especially because of the recipes - many of them not to be found in the standard cookery manuals - appended to each chapter.
Collingham's fundamental aim is to chronicle "a history of the Indian subcontinent" and its various rulers through its food. Beginning with the Moghuls, she shows how different kinds of cuisine took root in different regions and social levels, without any becoming the national cuisine. Unlike many food writers, she does not imagine that there is some unchanging and authentic "Indian" cuisine waiting to be discovered. Instead, she begins with a clear discussion of the sheer complexity of cuisines in India itself, now as well as in the past.
Innumerable variations are to be found even within one region. Growing up in Calcutta, I learnt, for instance, to appreciate the differences between the food of eastern and western Bengal. Even within the sub-variety of eastern Bengali cooking, the cuisines of particular towns and religious communities were supposed to have unique features. The vegetarian dishes developed by the Hindus of Dhaka, for instance, were considered the most sophisticated of their kind.
All the regional cuisines of India have such sub-varieties. Add to those the many culinary differences of class, gender, marital status, caste and religion, and you will see why no cookery book could ever hope to do justice to them.
This diversity became even more marked during the Raj. The British loved curry but, then as now, they and their Indian chefs experimented with indigenous recipes, producing a vast new repertoire of Anglo-Indian dishes. The simple peasant recipe of khichri, a mixture of boiled rice, lentils and a few spices, turned for instance into kedgeree (rice, fish and hard-boiled eggs): the favourite breakfast dish of Anglo-Indians and even the British aristocracy at home.
Anglo-Indians and their chefs also developed many condiments, such as Worcestershire Sauce, now so associated with the making of Bloody Marys that hardly anybody recalls its Indian origin. Such innovations are not special cases; they are integral to the history of curry.
Of course, even the doughtiest defender of culinary experiment must feel some qualms beholding the fate of curry in modern Britain. The "Indian" restaurants established by immigrants from Sylhet, a region of Bangladesh never known for the excellence of its food, may well be shining symbols of immigrant entrepreneurship. But should the reputation of one of the world's great cuisines rest on the greasy and garish gloop they serve?
Further down the food chain, what is one to make of sachets of "curry sauce" at the local chippy? Such anxieties are understandable but, as Collingham shows, Indian food has travelled so well and so far largely because it has always embraced change while managing to remain recognisably Indian. Wherever South Asians have gone, they have taken their cuisines with them and developed them in response to local conditions. Indian food in Fiji is obviously not the same as in Vancouver, Lucknow or Port of Spain, but it all belongs to the same enormous family, which has always been so variegated that it can easily accommodate variants and occasional deviants without fuss and without undermining its own identity.
The future of curry, Collingham rightly suggests, is safe for as long as the boundaries of "Indian food" remain flexible - and as long as its exponents respond adventurously to new environments and their challenges.
Chandak Sengoopta teaches history at Birkbeck College, London, and is the author of 'Imprint of the Raj: How fingerprinting was born in colonial India' (Pan)