How much in old money?

Don't know why, but the question arose on telly the other day as to how much 100 guineas was.  Well the answer is £105.00.  The guinea has a long history and for much of it was pegged to the value of gold, and thus its monetary worth varied as the price of gold went up and down, but it eventually settled at 21s - that is one pound, one shilling.  Professional men like doctors and lawyers, and upper-class merchants like art dealers or high-class tailors and the like, would employ a clerk to do their book-work for them and would charge for their services in guineas - the idea being - one pound for me and a shilling for my clerk.