A cornerstone of British justice was that once you were acquitted of a crime, you were in the clear. No-one could be put in double jeopardy for the same offence. This has now been changed to allow a retrial if "compelling evidence" emerges. The thinking is to catch people who "escape justice" the first time if scientific advance or new testimony emerges to make a conviction more likely.
This is a mistake. There was a good reason for the double jeopardy principle. It prevented the law playing cat and mouse with people, trying them again and again in the hope of securing a guilty verdict, maybe with a tougher judge or a different jury. The fact that they only had one shot at it encouraged the state to be rigorous in its preparation. With multiple attempts they can afford to be sloppier in their approach. More to the point, if a person could not be found guilty the first time "beyond any reasonable doubt," they were clear to continue with their lives without fear of state harassment. The abolition of double jeopardy means that this is no longer true.