Obama made up story about his grandfather being tortured by the British?

As the UK Daily Mail notes this claim about torture is inaccurate just "like most of the President’s own memoir":

But Maraniss, who researched Obama’s life in Kenya, Indonesia, Hawaii and the mainland United States, found that there were ‘no remaining records of any detention, imprisonment, or trial of Hussein Onyango Obama’. He interviewed five people who knew Obama’s grandfather, who died in 1979, who ‘doubted the story or were certain it did not happen’.
This undermines the received wisdom that Obama’s grandfather was a victim of oppression, an assumption that has in turn fuelled theories that Obama harbours an animus towards Britain based on a deeply-rooted rage about the way Onyango was treated.John Ndalo Aguk, who worked with Onyango before the alleged imprisonment and was in touch with him weekly afterwards said he 'knew nothing' about any detention and would have noticed if he had gone missing for several months.Zablon Okatch, who worked with Onyango as a servant to American diplomats after the supposed incarceration, said: ‘Hussein was never jailed. I know that for a fact. It would have been difficult for him to get a job with a white family, let alone a diplomat, if he once served in jail.’Charles Oluoch, whose father was adopted by Onyango, said that ‘he did not have any trouble with the government in any way'.Dick Opar, a relative by marriage to Onyango and a senior Kenyan police official, gave what Maraniss judged to be the most authoritative word. ‘People make up stories,’ he said. ‘If you get arrested, you say it was the fight for independence, but they are arrested for another thing. . ..