Barack Obama is no admirer of British colonialism, to judge from his writings, but the discovery that the British authorities tortured his grandfather may well deepen any animosity.

In his bestselling memoir, Dreams from My Father, Mr Obama does not conceal his disdain for British imperialism and his anger at what he sees as the brutality of colonial rule in Kenya. Almost every reference to Britain or the British is negative.

He briefly describes Hussein Onyango Obama’s detention by the British, but in a way that suggests he either did not know, or did not wish to reveal, the extent of his grandfather’s suffering at British hands.

Mr Onyango died in 1979, nearly a decade before the President-elect made his first visit to Kenya, but his subsequent account of that trip is deeply coloured by what he learnt of his grandfather’s life under colonial rule. Looking over Mr Onyango’s domestic servant record papers, for example, he notes wryly that one white employer declared that his grandfather was “found to be unsuitable and certainly not worth 60 shillings a month”.

When Mr Obama travels by train to western Kenya to visit the ancestral village, he observes that the building of the Mombasa-Lake Victoria railway cost “the lives of several hundred imported Indian workers”.

Mr Obama has nothing good to say of the colonial era, which he summarises as “the manipulation of colonial boundaries, the displacements, the detentions, the indignities large and small”.

Even the British man who sits next to him on the plane to Nairobi is depicted as casually racist, referring to the “Godforsaken countries” of Africa.

“I was just angry,” writes Obama, “because of his easy familiarity with me, his assumption that I, as an American, even a black American, might naturally share in his dim view of Africa.”

Mr Obama is particularly scathing of white tourists reliving the myth of Happy Valley in Kenya. “Kenya, without shame, offered to recreate an age when the lives of whites in foreign lands rested comfortably on the backs of the darker races,” he writes.

Here a white man “could be served by a black man without fear or guilt . . . and if he felt a touch of indigestion at the sight of leprous beggars outside the hotel, he could always administer a ready tonic. Black rule has come, after all. This is their country. We are only visitors.”

There is no surviving photograph of Hussein Onyango, but his identification card or “Native Registration Ordinance”, described bitterly by Mr Obama in his book, gives an idea of how the colonial authorities chose to depict their African staff and subjects: “Complexion: Dark; Nose: Flat; Mouth: Large; Hair: Curly; Teeth: Six missing . . . ”

To Mr Obama’s ears, that description must seem grimly close to the way that slaves were catalogued for sale in the antebellum South.

Times Recommends

• 'New York has lost its edge'
• Copenhagen will fail – and quite right too
• More than 17,000 new underwater species found