There isn't a "Supreme Court" in the British system, and I've always found it curious that the rebels created something original. Federal judges are understood to be part of the Justice department, and if one appeals past, say, a Circuit Court of Appeals the case lands on the floor of the House of Lords. The Upper House is the court of last resort - in the American case, the Senate.
It is a different, and in my opinion far clearer and more accurate, understanding of the function of a "supreme" court. If it was possible to decide a case by interpreting existing black-letter law, that case would never make it that far. The highest court creates laws that are urgently needed but which the legislature has for whatever reason not debated and written. When existing law is found to be an inadequate answer, the legislative body has to quit ducking the question and write the needed law. Complaints about "activist judges" may or may not have merit in regard to lower courts and circuit courts, but when referring to the highest court of the land they are manifestly asinine; a "supreme" who is not "activist" in one direction or another is unqualified for their office.