The British legal system is adversarial. This implies that in a trial, the jury and the judge remain entirely neutral. Although judges can ask for clarification, they do not get involved in questioning witnesses or finding evidence.
The prosecution and the defence present their cases and the judge ensures that there is fairness. After all the parties have been heard, the jury or the judge decides if the defendant is guilty or not. In criminal cases, the degree of proof is usually beyond reasonable doubts while civil matters are determined based on the balance of probability