Judges do both. Judges interpret the statue law and they make the common law. There are two types of law one would be the primary law, which is also known as the statue law and the secondary law, which is also known as the common law. For the primary law it is created by the legislature, which is the parliament as the parliament has the power to make the statue because the people elected them. So the judges interpret the primary law, which was created by the legislature. For the secondary law, which is the common law, the judges make this common law base on the cases and it is developed extremely slow and cautious and incremental bit by bit.as they would need to consider the principle and the loopholes in the law that they might be create or they could also make it so that it only applies in that particular case. Primary law always trumps secondary law meaning if there is a primary law the court should always use the primary law for the case. If there isn’t any primary law for the particular case then the court shall use the secondary law by referring the previous cases. They would interpret the existing statue law and the previous decision of higher ranking courts from there they would then decide whether to use the existing law or create the law by making legal principles which courts lower down the hierarchy are bound to follow depending on the case which they are attending to. This is so that they could be consistent with their ruling and it would be fair.
Back in the past, when the king’s representatives travelled from London to the provinces, checking the procedures in the local courts. They became the judges as time pass and the decisions that they make in the court that they trial was then recorded down and subsequent judges that passes through the town and trialed the case use the same decisions that the previous judge made so as to remain consistent on the law and so as time passes
References: 978-9-81068746-5, (2011), Introduction to Commercial Law, SMa Institute of Higher Learning, Joy Tan, Business Law (5th edition), Ewan MacIntyre, Business Law (4th Edition), Andy Gibson and Douglas Fraser