“Jim was a forthright and inspirational leader much esteemed by the people in the communities he served,” says former patrol officer Will Muskens, who served under him in the 1960s. He was one of the “very special group of Australian explorers who endured considerable hardship and deprivation (not to mention danger) leading government patrols into the previously uncontrolled and unexplored interior of the New Guinea mainland”.

The beautifully produced Middle Kingdom, described by the author as “a huge beast of a book”, offers Sinclair’s final and splendid ­fanfare to a mammoth feat of nation-building, particularly in the 30 years of change between the end of the war and PNG’s independence in 1975.

The large-format, hard-cased book, rich in information and with hundreds of photographs, many taken by Sinclair, offers the story of the misty and mysterious PNG Highlands from before the days of early Australian colonial exploration (which occurred only in the 1930s) to the colonisers’ lachrymose farewells when the new nation, one of the last ­significant colonies to be relinquished, achieved independence.

Sinclair was born in Dubbo, NSW, and in 1947, aged 19, joined the administration of what was then the Australian Territory of Papua and New Guinea. After attending an orientation course at the Australian School of Pacific Administration in Sydney, he landed in PNG in August 1948 as a cadet patrol officer, pikinini kiap in pidgin English. These young men, selected for their enterprise and physique, were tasked to explore, placate and introduce government to PNG’s 800 tribes.

Sinclair conducted exploratory and pacification patrols in the Highlands, opening Koroba station in 1955 and Lake Kopiago base camp in 1956, and exploring uncontrolled tribal lands in the far west of the territory. He steadily rose through the kiap ranks, finishing his career in 1975 as the last Australian district commissioner presiding over the fertile, populous and sometimes volatile Eastern Highlands region.

What he saw and experienced during his 26 years in the service of Pax Australiana was to influence and engage him for the rest of his life. His first book, Behind the Ranges, ­appeared in 1966, telling the story of his early exploratory patrols. It set a standard for thoroughness in research, insight and literary craftsmanship still evident 50 years later when he sat down to write Middle Kingdom.

Behind the Ranges almost came to nothing. Not long after he married Jan in 1959, Sinclair was struggling with the manuscript and doubted his capacity to complete the book he had envisaged. Late one afternoon, Jan saw him tearing apart a huge sheaf of papers held together by long bolts. She asked what he was doing and Sinclair replied, “Just some stuff I’ve written; everyone in New Guinea writes stuff.” Jan Sinclair stopped the destruction and ­prevailed on him to continue the task.

Sinclair’s first six books were published while he was still in PNG and, when he retired from the administration in 1975, it was an easy transition to full-time authorship and the prolific recording of colonial history. That said, his works remain unknown to most Australians who, after PNG independence, tended to lose interest in our nearest neighbour and our one great colonial experience.

Tony Crawford, whose Adelaide imprint published Middle Kingdom, first met Sinclair in the 70s, when Crawford worked at the PNG National Museum.

“He was after some photographs for one his early books on the art of Papua New Guinea and we built up a wonderful rapport as publisher and author that lasted till the last day,” Crawford says. “His superb photography and knowledge of PNG instilled a valuable history in many people worldwide: academics, historians, travellers and those who lived in PNG during the good old times.”

This 40-year relationship between publisher and author reaches its apotheosis in Middle Kingdom, which Crawford has produced with care and acumen.

The book fluently guides the reader from the early days of exploration (illustrated with many historic photographs), through the ­Pacific War, the greater urgency of post-war development and the challenges and turbulence of an independence that, in the view of many colonisers and most of the Highlands people, came far too early.

Middle Kingdom is as detailed and well ­researched as a history should be, but the ­anecdotes, illustrations, maps and superb index offer an outstanding experience for the reader. It is a book for every location between the coffee table and the university library, a wonderful compendium of a critical time in the history of PNG written by a man who understood the significance of the period in which he was both an important participant and an acute observer.