Truly mountainous feats of derring-do

As recently as the mid-19th century, the state of cartography in Britain was such that the Royal Geographical Society still had no firm idea of the exact location of Lhasa, the capital of Tibet. Although this seems of little importance now, the possibility of Russian imperial expansion into British India through Tibet was a constant headache for the Whitehall mandarins of the day. As the two empires played out their game of espionage and diplomatic muscle-flexing, cartographic knowledge of this harsh mountain range assumed ever-increasing significance. The blanks on the maps of Himalaya and the surrounding regions represented an invasion route for the Russians. It was a matter of national security, and something had to be done about it.

British spies had tried to infiltrate the Indian border states in search of this knowledge, only to find their path barred. When attempting to enter Tibet, agents were routinely turned back, imprisoned and, on occasion, brutally murdered. But in the 1860s Captain Thomas Montgomerie came up with the idea of using specially trained local surveyors, rather than undercover British military politicals, to work covertly to map the region, gather valuable data about the Tsangpo and Brahamaputra Rivers and discover potential Russian invasion routes.

These men became known as pundits, and their story is the subject of Jules Stewart's excellent Spying for the Raj . The men came from disparate origins. There was a village school headmaster from the hills of Kumaon, a Bengali engineering graduate, a Sikkimese Buddhist monk, an illiterate tailor's assistant from Darjeeling and so on. And theirs is one of the great tales of the Great Game, packed with mind-boggling danger, devotion to duty and stranger-than-fiction derring-do. It was Rudyard Kipling, of course, who fictionalised the pundits in his novel Kim . And it is Kipling who best describes the motivating force behind these extraordinary men: "From time to time, God causes men to be born - and thou art one of them - who have a lust to go abroad at the risk of their lives and discover news... These souls are very few, and of these few not more than ten are of the best."

The pundits get their name from the popular Hindi term for "sage" or "wise man", a word derived from the Sanskrit paita , meaning "learned" or "scholar". Even though the New Oxford English Dictionary fails to make the distinction clearly, "pundit" should not be confused with the more familiar "pandit", an honorific roughly equivalent to "Sir". And although the word is probably best known in India today as the name of a Toyota family saloon car, the pundits of Stewart's Spying for the Raj were to play a key role in the final acts of the Great Game.

Disguised as traders or monks, the pundits taught themselves to measure immense distances with breathtaking accuracy by counting their own paces (despite the nature of the terrain, they had the freakish ability to walk at exactly 2,000 steps per mile). They kept count of these distances using modified Buddhist rosaries, navigated by the stars and calculated altitude by observing the boiling point of water. They were often in the field for years on end, tortured, imprisoned, sidetracked (gambling, drinking, women and so on) or struck down by disease. The hardships they endured in total anonymity, and for no more than a pittance, speak of an era when duty and service were more important than personal comfort or material wealth. The story of Pundit Kintup, the hapless tailor who never once deviated from his aim to send 500 tagged logs down the Tsangpo river in an attempt to confirm a link with the Brahmaputra, has now passed into legend. Captain G. F. T. Oakes of the Survey paid tribute to Kintup's determination as showing "the greatest pluck", commenting that his experiences were "a romance of the Survey of India".

But the best known of the pundits was the first. Nain Singh was an undisputed genius of exploration, a man who earned the praise of Sir Clements Markham, one-time Secretary of State for India and president of the Royal Geographical Society. Markham wrote in his memoir of the Survey: "The journey performed between July 1874 and March 1875 by the Pundit Nain Singh... is the most important, as regards geographical discovery, that has been made by any native explorer." As well as being made Companion of the Indian Empire, Singh also became the only pundit to be awarded the highest honour the Royal Geographical Society can bestow, the Patron's Medal, "for his great journeys and surveys in Tibet and along the Upper Brahmaputra".

In researching Spying for the Raj , Stewart - who is currently writing The Savage Border , a history of the North-West Frontier - spent time in Dehra Dun, the headquarters of the Survey. While there he had unique access to original documents of the era and maps of the area, as well as the chance to experience first hand the actual theodolites, compasses and prayer wheels used by the pundits. He also interviewed several of the current survey officers, as well as R. S. Rawat, a retired survey officer and descendant of Singh. This extensive fieldwork gives Spying for the Raj an extra dimension: as well as being well researched and stylishly written (Stewart is a former Reuters journalist), it is authentic and exciting.

Although not aimed specifically at the academic community, comprehensive footnotes and a decent bibliography make accessible primary source material used by Stewart in India. Of equal importance, Spying for the Raj is almost certainly the first book about the pundits for the general reader and as such it is an important addition to the canon of the literature of the subcontinent, destined to become required reading for anyone interested in a territory more usually associated with Charles Allen and John Keay.

Nick Smith is a former editor of Geographical, the magazine of the Royal Geographical Society.