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The Common Serjeant must not be confused with the Common Sergeant . . .
as Mary says here. And he must definitely not be confused with the Kings Serjeant who was the most senior of the Serjeants-at-Law, the select group of lawyers, from which Judges were selected. Not to mention at various periods the First Serjeant and the Prime Serjeant.
They congregated around Serjeants Inn off Chancery Lane. I used to nip through the old courtyard on my way to lightbulb changing duties in Chancery Lane some years ago. In true English fashion the name is now commemorated in the area as a pub. The practice of appointing Judges only from the ranks of Serjeants was abolished in 1875. All that remains in the modern system is the post of Common Serjeant who is the deputy to the senior permanent Judge at the Central Criminal Court, Old Bailey. That Judge has the title Recorder of London. And he should not be confused with an ordinary recorder, who is a lawyer, like Cherie Blair, who sits occasionally as a part time Judge on criminal trials in the Crown Court.
The Old Bailey is treated these days as one of the many centres of the Crown Court of England and Wales, which is the higher of our criminal courts, but because of its history there are a couple of oddities about its practice and jurisdiction.