Question:  Long John Silver was quartermaster under a fictional 18th-century pirate captain created by what writer?

Context paragraphs:
The Adventures of Long John Silver: The Adventures of Long John Silver is a TV series about the Long John Silver character from "Treasure Island".  It was made in 1954 in colour in Australia for the American and British markets before the development of Australian television.

Long John Silver (film): Long John Silver, also known as Long John Silver's Return to Treasure Island, is a 1954 American-Australian Adventure film about the eponymous pirate from "Treasure Island", starring Robert Newton as Silver and Rod Taylor as Israel Hands.

Long John Silver: Long John Silver is a cunning and opportunistic pirate who was quartermaster under the notorious Captain Flint.  Long John Silver had a pet parrot called Captain Flint, often seen sitting on his shoulder where she would nibble on seeds.  Silver claims to have served in the Royal Navy and lost his leg under "the immortal Hawke".  "His left leg was cut off close by the hip, and under the left shoulder, he carried a crutch, which he managed with wonderful dexterity, hopping about upon it like a bird.  He was very tall and strong, with a face as big as a ham—plain and pale, but intelligent and smiling."  ("Treasure Island" (1883) by Robert Louis Stevenson page 82).  He claims to have been the only man whom Flint ever feared.  Like many of Stevenson's characters, there is more than a modicum of duality in the character; ostensibly Silver is a hardworking and likeable seaman, and it is only as the plot unfolds that his villainous nature is gradually revealed.  His relationship with Jim Hawkins, the novel's protagonist and narrator, is interesting, as he serves as a mentor and eventually father-figure to Jim, creating much shock and emotion when it is discovered that he is in charge of the mutiny, and especially when Jim must confront and fight him later on.  Although willing to change sides at any time to further his own interests, Silver has compensating virtues: he is wise enough to pay attention to money management, in contrast to the spendthrift ways of most of the pirates, and is physically courageous despite his disability; for instance, when Flint's cache is found to be empty, he coolly stands his ground against five grown men despite having only Jim, a boy in his teens, to back him.

Captain Flint: Captain J. Flint is a fictional 18th-century pirate captain who features in a number of novels, television series, and films.  The original character was created by the Scottish writer Robert Louis Stevenson (1850-1894).  Flint first appears in the classic adventure yarn "Treasure Island", which was first serialised in a children's magazine in 1881, and later published as a novel in 1883.

Pirates in popular culture: In English-speaking popular culture, the modern pirate stereotype owes its attributes mostly to the imagined tradition of the 18th century Caribbean pirate sailing off the Spanish Main and to such celebrated 20th century depictions as Captain Hook and his crew in the theatrical and film versions of "Peter Pan", Robert Newton's portrayal of Long John Silver in the 1950 film of "Treasure Island", and various adaptations of the Eastern pirate, "Sinbad the Sailor".  In these and countless other books, movies, and legends, pirates are portrayed as "swashbucklers" and "plunderers."  They are shown on ships, often wearing eyepatches or peg legs, having a parrot perched on their shoulder, and saying phrases like "Arr, matey" and "Avast, me hearty."  Pirates have retained their image through pirate-themed tourist attractions, traditional film and toy portrayals of pirates, and the continued performance and reading of books and plays featuring pirates.

Long John Silver's: Long John Silver's LLC is an American fast-food restaurant chain that specializes in seafood.  The brand's name is derived from the novel "Treasure Island" by Robert Louis Stevenson, in which the pirate "Long John" Silver is one of the main characters.  Formerly a division of Yum!  Brands, Inc., the company was divested to a group of franchisees in September 2011.

Thomas Anstis: Thomas Anstis (died April 1723) was an early 18th-century pirate, who served under Captain Howell Davis and Captain Bartholomew Roberts, before setting up on his own account, raiding shipping on the eastern coast of the American colonies and in the Caribbean during what is often referred to as the "Golden Age of Piracy".

Kit Taylor: Kit Taylor (born 1942) is an Australian actor, the son of Grant Taylor.  He made his acting debut as Jim Hawkins in the film "Long John Silver" (1954) and the associated TV series "The Adventures of Long John Silver".  He went on to have an acting career as an adult.

Space Pirate Captain Harlock: Space Pirate Captain Harlock (Japanese: 宇宙海賊キャプテンハーロック , Hepburn: Uchū Kaizoku Kyaputen Hārokku , also romanized as "Space Pirate Captain Herlock") is a manga series written and illustrated by Leiji Matsumoto.  It was serialized in "Play Comic" from 1977 to 1979, with the chapters collected into five "tankōbon" volumes by Akita Shoten.  The series follows the titular Captain, an outcast turned space pirate after he rebelled against Earth's Government and humanity's general apathy.

Space Pirate Captain Herlock: The Endless Odyssey: Space Pirate Captain Herlock: The Endless Odyssey, also known in Japan as Space Pirate Captain Harlock: Outside Legend - The Endless Odyssey, is an OVA of Space Pirate Captain Harlock.

Supporting paragraphs: Long John Silver Captain Flint
Answer: Robert Louis Stevenson