The U.K. was a major colonial power. Since the 1960s, many of the former colonies have achieved their independence but from time to time the colonial past comes back to haunt. The solicitors Leigh and Day have brought to public attention a claim by some elderly Kenyans in respect of appalling treatment they allege that they received at the hands of the Kenyan authorities when Britain was the colonial power. See this link. It seems that the British government is arguing that it is now nothing to do with them because of the international law doctrine of State Succession.
Of course, it is not unusual for a new (successor) State to assume authority over the territory of an old (predecessor) State. The transformation of a colony into an independent nation is one way in which this occurs and Kenya became independent in 1963. The International Law Commission has been considering the many aspects and problems of State Succession for many years.
It could be an interesting one this! I wonder if somehow it might eventually all get settled out of court?
See also Afua Hirsch writing in The Guardian 25th January 2010
Addendum 6th April 2011: "Kenyans sue for UK Colonial human rights abuses" - The Guardian. Also, "Mau Mau victims to give evidence at High Court" - Solicitor's Journal 5th April 2011.
Addendum 5th June 2013: The Guardian 5th June - reports settlement of the dispute but only after lengthy court proceedings