As the French naturalist Victor Jacquemont travelled around India he had to admire the dignified reserve of English imperial rulers. But he found that this quality cut them off not only from their despised subjects but also from the ‘pleasures of the heart’. Ironically in view of their French Huguenot name, this observation applies exactly to the ‘thoroughly anglicised’ members of the Du Boulay family, the ‘servants of empire’ whose letters form the basis of this book.

Sons of the Reverend James Du Boulay, a housemaster at Winchester between 1862 and 1893, they developed their ‘silent Wykehamist reserve’ at the public school which was also their home. The daughters, too, veered towards a decorous formal life. Phyllis entered an Anglican convent; Mary, ‘untouched by any caress’, became a Schools Inspector in South Africa; Isabel and her husband founded and ran Horris Hill Prep School, a spartan establishment which sent most of its products to Winchester.

The family letters consulted by the author, a grandson of the Reverend James, reflect the emotional reticence of their writers. Dry as they are, their interest lies as much in the imperial mentality they unwittingly reveal as in the historic events they describe. Battery officer Noel played up and played the game in two desert battles during the Gordon relief expedition of 1884-85. ‘Gubat was almost as exciting as Eton Match 1870,’ he wrote, ‘while at Abu Klea I had a sort of sensation of having been planted at football’. Noel often reports on ex-public schoolboys he encountered in Egypt and on later postings: the officer in charge of embarkation on the Nile was ‘an old Captain of Boats at Eton’ and the louche Wykehamist Edmund Backhouse helped him to list the treasures of Peking’s Summer Palace. He valued such contacts but never formed intimate relationships and spent his retirement in English hotels, ‘a favourite uncle’ of the author’s.

A less lonely existence was that of James Du Boulay, a ‘straight and taciturn official’ who became private secretary to the Viceroy of India, Lord Hardinge. James’ wife Freda, who ‘played the grande dame effortlessly’, was in India most of the time. She even kept the children there for longer than was customary, boasting that hers was ‘the most homelike house in India’. Yet personal details appear less in the couple’s correspondence than in the diary of the stuffy viceroy himself. James was more prone to dwell on ‘the relentless torrent of knotty questions’ facing him at a time of nascent Indian nationalism. Freda’s letters during the king-emperor, George V’s visit to Delhi in 1911 stoically describe her ceremonial role as lady-in-waiting to the queen, herself a royal automaton. They make no mention of the recent death of Freda’s baby son.

Most revealing about imperial racial attitudes are the letters Dick Du Boulay wrote from his ostrich farm in the Transvaal, where he was maddened by ‘the wily kaffir’ on whom he depended for labour. By contrast, his hard-working sister Mary found Africans ‘perfectly civil’ but was critical of ‘colonial’ families who were all too apt to show their feelings – ‘so different from our own home upbringing’.

The author himself clearly shared the family’s constitutional reserve. He shows his father Philip almost entirely in his public roles with the Egyptian Irrigation Service and the Salt and Soda Company, barely mentioning his late marriage to a former fiancée. ‘F.R.H.’ says nothing of his own childhood, some of which must have been spent in Egypt – for that might have revealed some secrets of the heart. As it is, this book is a bound copy of the stiff upper lip.

Vyvyen Brendon is the author of Children of the Raj (Weidenfeld and Nicolson, 2005) and Prep School Children: A Class Apart over Two Centuries (Continuum, 2009).