Mr Nyingi, 84, said he was arrested on Christmas Eve 1952 and detained for about nine years.
During that time, he was beaten unconscious in an incident in 1959 at Hola camp in which 11 men were clubbed to death.
He says he still bears marks from leg manacles, whipping and caning.
When I was released I would have nightmares about three times a week. I would dream about the murder of people at Hola. These nightmares continued for about four years.
When people talk about the Mau Mau or the colonial era I think about the terrible events I lived through. When these thoughts are triggered I get so sad and stressed about what happened that I develop a headache and I cannot work.
I feel I was robbed of my youth and that I did not get to do the things I should have done as a young man.
Government argues Mau Mau case is too old to go to trial
The Government has argued that too much time has passed to allow a fair trial over alleged atrocities by British authorities in Kenya in the 1950s.
Guy Mansfield QC said the Foreign and Commonwealth Office faced "irredeemable difficulties" with witnesses and documents to defend the claim.
Without those witnesses, and indeed with the necessarily limited recollections of those who do survive, the very complicated and difficult task of determining the competing factual positions cannot be fairly conducted.
There is a dearth of evidence which can be given as to what was in people's minds when they made decisions and sent or read telegrams or attended meetings or were told of matters or visited places.
Three Kenyans who claim they were tortured by British colonial authorities during the Mau Mau uprising in the 1950s will make their case for damages at the High Court today.
Hundreds of Kenyans have made similar claims, but these three are the only ones to be told they have a chance of winning. Their case rests in part on an archive of 8,000 secret filed that were spirited out of the country when Kenya gained its independence in 1963.
The British Government is expected to argue that the claims are time-barred and that the window of opportunity is shut.