Edit: sorry I misread your post and thought you meant the British Constitution. Never mind... but leaving the post up because it is informative.
The UK doesn't have an official Constitution in the way that the United States does. The British Constitution is uncodified, and evolved over time from many different documents and precedents. Examples being the Magna Carta (1215), Bill of Rights (1689), Human Rights Act (1998), judicial decisions such as the rule of law and limits on executive power, and unwritten but binding political practices such as the Prime Minister must be a member of the House of Commons.
British Courts also cannot invalidate acts of Parliament in the same way that the Supreme Court in the US can invalidate laws if it deems them unconstitutional. Parliament in the UK is sovereign, they can make or unmake any law and can't be struck down.
This was attempted during the US Civil War. Since there is no official option written into the US Constitution, its legality was disputed.
It was never decided in Court, instead the Battles of Fort Sumter and First Mananas/Bull Run started the Civil War. Deciding it in court would have been interesting, as a number of the Supreme Court Justices were sympathetic to the Confederacy, notably the Chief Justice Roger Taney. Instead, the Civil War ended with a Union Victory, Taney died in 1864 and was replaced by Salmon Chase, who helped establish the Republican Party and wrote Texas v White, a Supreme Court decision on secession.