In the most simple terms,
the Supreme Court held (a) that the UK government (and not the Malaysian government) was responsible for the actions of the soldiers and (b) that the government was not under any legal obligation to hold an inquiry. Nevertheless, it is clear from the court's judgment (as well as the judgments of the courts below) that the "trying to escape" stance cannot be truly supported. The moral victory rests with the appellants who are relatives of the victims.
Lady Hale (dissenting) would have allowed the appeal on the basis that the Secretaries of State did not take into account all the possible purposes and benefits of an inquiry and so they had reached a decision that was not one which a reasonable authority could reach - paras. 309-13 of the judgment. This is the classic Wednesbury reasonableness test adopted by the common law.
The solicitors in the case - Bindmans LLP - have issued a Media Statement following the Supreme Court's judgment.
The families’ lawyer, John Halford of Bindmans LLP said:
An interesting post on the case is at UK Constitutional Law Group Blog - Rylatt and Tomlinson: Neuberger's Novelties: Keyu and the substantive review debate.