Sharpe first encounters Lord Pumphrey in 1807 and he was described as about thirty years old (Sharpe's Prey : Chapter 3). He was very thin and appeared frail and bird-like. He dressed lavishly, wearing a silver edged coat, trimmed with lace, and sported a black velvet beauty patch on his cheek. He was an exquisite, and his appearance did much to hide the cold-blooded and ruthless intellect behind the mask.
Lord Pumphrey attended Eton with The Honorable John Lavisser where he acted the part of Ophelia to Lavisser's Hamlet in a school production (Sharpe's Prey : Chapter 3). Although nothing is known about how the character came to work at the Foreign Office, he appears to be of the diplomatic corps or perhaps even a general "clean up man", responsible for cleaning up mistakes and tying up loose ends.
When it is discovered in Sharpe's Prey that the British agent in Denmark, Ole Skovgaard, gave the names of British agents abroad to his daughter Astrid, and that neither are willing to leave Copenhagen to escape the approaching French, Pumphrey does not hesitate to order their deaths in order to keep the information from passing into the wrong hands.
This act has lasting effects, Astrid had been Sharpe's lover and his discovery of the facts behind her death permanently sours what had hitherto been a cordial and even friendly relationship between the two Sharpe and Pumphrey. Sharpe offered to cut Pumphrey's throat for him, as he had ordered for Astrid, if he did not pay Caterina for her letters. When he saw Pumphrey's hand twitch toward a pocket, he laughed and asked if he really thought he could fight. Pumphrey did not make any further defensive moves. He paid, and Sharpe burned the letters, denying Pumphrey his "small lever to hold over the Wellesley family forever" (Sharpe's Fury). Pumphrey acknowledges Sharpe as a skilled player of the game of back alley give and take.
In addition, to his tendency to have people killed; Pumphrey has extremely sticky fingers where government funds are concerned. He appropriates a good portion of the recovered gold in Sharpe's Prey and also is guilty of skimming money from Henry Wellesley in Sharpe's Fury.
From Cornwell's descriptions, Pumphrey is affected, ironic, and urbane; he is also a homosexual and is apparently attracted to both Sharpe and Sir Arthur Wellesley. His behavior could be considered outrageous for the period: he tells Sharpe and Major Hogan that "Sir Arthur makes me go weak at the knees" (Sharpe's Havoc : Chapter 9) - but he somehow manages to get away with it, hinting at the amount of influence that he either exercises himself, or that backs him back at Whitehall.
- Pumphrey's full name is given as William Pumphrey though he is referred to as "Lord Pumphrey", indicating that he is the eldest son of a peer or a peer in his own right.
- Characters who address Pumphrey familiarly often call him "Pumps"; Sharpe does this sarcastically once in Fury when Pumphrey presumes too much.
- He was apparently intended for army service by his father until it was determined that he was too frail for such a barbaric occupation (Sharpe's Prey : Chapter 3).
- He is called a "molly" behind his back, a contemporary term of derision for effeminate or homosexual men.
- Though he is always referred to in canon as a "lord", his exact title and rank are uncertain. Given the rules of style and usage for the Peerage of England/Great Britain/Scotland/Ireland/United Kingdom though, there are several possibilities that might apply to Pumphrey. If his father is still living, then his title is merely courtesy and he is, in fact, a commoner. If, however, his father is deceased, then he is a peer in his own right. Because Pumphrey appears to be the character's surname as well as his title, one may assume that he holds a baronage, viscountcy, or earldom (though there is precedent for marquesses whose titles have been taken from their surnames instead of a geographical location.) However, because Pumphrey is never referred to by a specific rank in canon, it is safe to assume that he is most likely a baron (either by right or courtesy) because barons are never referred to as such in speech or writing within the British system.