Little, if anything, is written on exactly how the role of a Barristers’ Clerk came into being, so it is difficult to be precise as to exactly when & how they developed, and there are many different stories. The general consensus is that the Bar Clerk was originally similar to the Bob Cratchit figure from Charles Dickens’ A Christmas Carol, working for an individual barrister in his Chambers and was cross between a secretary, agent, manservant & housekeeper. Early literature suggests that the Clerk even lived within the barrister’s Chambers.
One story is that the Clerk organised everything including the supplies for the Chambers. He made his money by haggling with suppliers and obtaining the supplies (such as candles) for less than the allowance for them that he was given by his employer, and the difference supplemented his earnings. This became known as “candle money”.
Over time more formal agreements for remuneration were reached. The usual one, up until decimalisation in 1971, was for the Clerk to have a separate fee paid by the client. The Clerk would agree their barrister’s fee in guineas (pre-decimalisation there were 20 shillings in a pound and a guinea was £1 and 1 shilling). The pounds were for the barrister, and the shillings were for the Clerk, and they were billed separately. The client knew that by having a separate fee for the Clerk, their interests were protected by him (and Clerks were always a “him” in those days), as the Clerk would always operate in the client’s interest even if, it seems, that might not always be in the best interest of his principal.
I can even remember hearing a previous Senior Clerk over-ruling his Member of Chambers by saying that he earned his Clerks’ fee from the client by protecting his interests, and even though the best interests of the client were served by fixing an urgent date that was inconvenient to his barrister (who was unavailable for a long period), this was what he was required to do. He won the argument with the barrister, who being a gentlemen, accepted the principal of it. Times have changed a lot since then, and I am not sure matters would have followed the same course now.
When guineas were phased out in the seventies, it became traditional for the clerks to be paid 10% of the barrister’s fees, but for years many Clerks still viewed the whole fee as simply containing their Clerks’ fee, rather than them earning a percentage of their principal’s fee. Over time, as Chambers grew larger, the percentage reduced and may even these days be represented by a simple performance related annual bonus. Some self-employed Clerks still work on a percentage only arrangement.