You do understand that the people in the “English government” today (presumably you meant British) are not the same as in the 1950s.
At some point all of the criminals who did the thing in the past are dead.
Institutions can't act, because they have no brains or hands: only human beings can. You can't convict an institution of a crime, nor put it in prison.
Besides, we're talking moral responsibility not legal.
The only entities that can take actions of any kind are human beings.
Furthermore, hold responsible in this context means basically to acknowledge that the past actions were wrong, which is a pretty low bar as far as responsibility goes.