Explained
here.
Acts of Parliament, as we were taught by the venerable Dicey, are the highest form of law, within the hierarchy of sources of the law of England. However, none of them, according to his thinking, enjoyed a higher legal status than any other. Influenced by the legal philosopher John Austin’s views on the nature of sovereignty, Dicey regarded it as impossible for the legislative authority of Parliament to be limited by preceding Acts: “That Parliaments have more than once intended and endeavoured to pass Acts which should tie the hands of their successors is certain, but the endeavour has always ended in failure,” he wrote (Law of the Constitution, p.65). Dismissing what may have been thought of as one contender for higher status with a degree of mockery, he argued that “neither the Act of Union with Scotland nor the Dentists Act 1878 has more claim than the other to be considered a supreme law".
Dicey lived long enough, by the way, to see the establishment of the Irish Free State, and the enfranchisement of women, both of which he deprecated very strongly. The Act of Union - Scots tend to call it the Treaty of Union - is still there.
I am unaware of the current status of the Dentists Act 1878.
ETA. I looked it up.
https://en.m.wikipedia.org/wiki/British_Dental_Association. Fascinating.