A more thorough explanation:

A serjeant-at-law was a type of barrister in English law who had achieved the highest degree of the legal profession. They had the exclusive privilege of practicing in the Court of Common Pleas until 1846. Every judge of the common-law courts was required to be a serjeant-at-law until the Judicature Act of 1873. The rank was gradually replaced by that of Queen's Counsel.

• John was a serjeant-at-law and had the exclusive right to practice in the Court of Common Pleas.
• Before the Judicature Act of 1873, every judge of the common-law courts had to be a serjeant-at-law.

These examples illustrate how a serjeant-at-law was a highly respected and exclusive type of barrister in English law.

Serjeants' Inn was a building on Chancery Lane in London that housed the Order of Serjeants-at-Law. The building was sold and demolished in 1877.

• The Order of Serjeants-at-Law used to be housed in Serjeants' Inn on Chancery Lane.

This example shows how Serjeants' Inn was a physical location associated with the Order of Serjeants-at-Law.