“We only went to Kenya because a Nairobi businessman fumbled in his jacket pocket.” So begins Nicholas Rankin’s hybrid of history and memoir focused on the Mau Mau uprising in the 1950s. The businessman’s car keys “snagged the trigger of his Beretta, and he shot himself in the stomach. My father got his job.”

Historians don’t write history, they curate it, and in Trapped in History Rankin challenges his own childhood absorption of propagandistic accounts of Britain’s imperial past. Nearly 70 years after his arrival in Kenya from Sheffield as an intensely curious boy, Rankin, a former BBC World Service producer, writer and consummate storyteller with a flair for drama, has composed an insightful tale of hubris in colonial east Africa, underpinned by rigorous research.

When, in 1953, Rankin’s stockbroker father, James Tennant Rankin – always known as Tennant – told his pregnant wife, Peg, that he’d been offered a job as general manager of Buchanan’s Kenya Estates, at a time when the country was in a state of emergency, Peg’s immediate response was: “When do we leave?” The adventurous couple with three young children in tow – Rankin was three years old – arrived in 1954 in the middle of Operation Anvil with British soldiers patrolling the capital and detaining thousands of Kenyans suspected of sympathies towards the Mau Mau anti-colonial armed uprising.

The credits of relocating for nine years to this “beautiful country [but] contested land” outweighed the deficits. For the Rankins, as for so many who escaped dreary postwar Britain, Kenya provided a social upgrade, though it came with the risk, as CLR James once noted, of finding yourself “an aristocrat without having been trained as one”.

Tennant’s first car, chauffeured by a bemedalled former soldier of the King’s African Rifles, was “a limousine with louvred blinds in the rear window”, and on occasion Tennant would sport a “stiff satin cummerbund” befitting a gentleman. But all was not well; among Tennant’s gin-soaked contemporaries, anger masked disillusionment, ennui and the whispered fear of Mau Mau oaths.

Early on, a tension arises in the book between the historian’s demand for circumspection and the memoirist’s need for candour. While Rankin doesn’t shy away from self-revelation, he defers to older writers such as Margery Perham, the Rhodes scholar who first travelled to Nairobi in 1930, for their remembrance of the times. Perham observed that affluent white people in Kenya – men such as Tennant, who was a heavy drinker and gambler – suffered from “a subtle kind of demoralisation, which the victims cannot recognise, for themselves and their children”. It was a sentiment that still haunts Rankin.

Mining his own recollections elicits a tug of constant shame in his complicity, even though an innocent child, in a social order where any black man would be called “boy” and where a spurious allegation of “menacing a white woman” might result in being flogged with a hippopotamus-hide whip.

Though the book is part memoir, Rankin is keen to include a plurality of voices, including Ngũgĩ wa Thiong’o, whom he describes as Kenya’s greatest author, and especially other Africans previously eclipsed in the romanticised presentation of Britain’s civilising mission in the colonies. At one point, laying out the charge sheet of failings in Kenya, Rankin focuses on the Kikuyu, the country’s largest and most widespread single tribe, and enlists the help of pioneering Kikuyu writer and nationalist Parmenas Mockerie. In his remarkable book An African Speaks for His People (1934), Mockerie politely upbraided those exhibiting the common British mindset that the interests of white European settlers, worthy custodians of the land, were paramount.

The dispute over land is front and centre in Trapped in History; Britain’s failure to fully accept the Kikuyu concept of ownership and squatting rights vexed local Africans. A colonial policy of displacing them from ancestral lands and into waged labour, working for British settlers, was often contested, but largely went ahead anyway. The seeds of African discontent were also sown in the enforcement of the despised registration system, the kipande “neck box”. “In the name of social control,” writes Rankin, “human beings were being ordered to wear the identification collars of dogs.”

Racial humiliations were unending. Rankin highlights a 1930s account from Perham about the injustice meted out to a local leader who, appealing against a two-month sentence for holding a prohibited meeting, was rewarded with a longer two-year sentence. The silence of the Kikuyu listening carefully to the white judge condemning their leader “gave me a shiver of apprehension for the future”, wrote Perham.

Two decades later, Mau Mau militants killed dozens of white settlers and thousands of Africans deemed to be traitors and enemies, slashing, burning and mutilating them. The myth of British fair play, of being free from perpetuating such atrocities, though, has been skewered in recent years. In 2013, the UK government paid almost £20m in reparations to more than 5,000 surviving Kenyans who had suffered torture and abuse during the uprising.

Rankin’s portrayal of that violence is unflinching, with graphic testimonies such as from the then 15-year-old Jane Muthoni Mara, who, suspected of being Mau Mau, was horrifically sexually assaulted. She was at least spared the hangman’s noose that awaited more than a thousand of her compatriots.

In the suppression of the Mau Mau, Britain defaulted to blunt collective punishment, detaining thousands of suspects behind barbed wire, under observation from watchtowers. As a boy in Kenya, even if he’d been made aware of it, such action would have been unfathomable to Rankin. “What I could not conceive, as I sat on the floor of my father’s study in my shorts and shirt and Bata sandals, was that we, the brave British who I knew had won ‘The War’... were now building… concentration camps.”

In attempting to interrogate his privilege and divest himself of it, Rankin enters the territory of shameful histories mapped out by contemporaries such as Alex Renton in Blood Legacy and Rian Malan in My Traitor’s Heart. Such books seem marked by the authors’ determination to, in the words of the historian Peter Fryer, “think black”, and embark on an empathic journey towards self-abrogating enlightenment. In Trapped in History, Rankin frees himself, and perhaps readers, in curating a porous narrative that serves as an unforgettable distillation of Britain and Kenya’s complex and contentious shared history.

• Trapped in History: Kenya, Mau Mau and Me by Nicholas Rankin is published by Faber & Faber (£25). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply