Question: Which american born actor, director and writer starred in the rock music comedy This is Spinal Tap?
Context: Spinal Tap (stylized as Spın̈al Tap, with a dotless letter "i" and a metal umlaut over the "n") is a parody band spoofing the style of rock heavy metal groups.  The band first appeared on a 1979 ABC TV sketch comedy pilot called "The T.V. Show", starring Rob Reiner.  The sketch, actually a mock promotional video for the song "Rock and Roll Nightmare", was written by Reiner and the band, and included songwriter/performer Loudon Wainwright III on keyboards.  Later the band became the fictional subject of the 1984 rockumentary/mockumentary film "This Is Spinal Tap".  The band members are portrayed by Michael McKean (as David St. Hubbins), Christopher Guest (as Nigel Tufnel) and Harry Shearer (as Derek Smalls). Michael John McKean (born October 17, 1947) is an American actor, comedian, and musician, known for a variety of roles played since the 1970s.  He first came to national attention playing annoying neighbor Lenny Kosnowski on the sitcom "Laverne & Shirley".  In the mid-1990s he was a repertory cast member of "Saturday Night Live".  He has played roles in several Christopher Guest ensemble films, particularly as David St. Hubbins, lead vocalist and rhythm guitarist of the fictional rock band Spinal Tap in "This Is Spinal Tap".  He co-wrote the song "A Mighty Wind" (from the film of the same name), which won a Grammy Award, as well as "A Kiss at the End of the Rainbow" from the same film, which was nominated for the Academy Award for Best Song.  He plays Chuck McGill, brother of the protagonist of the AMC drama "Better Call Saul". This Is Spinal Tap (stylized as This Is Spın̈al Tap) is a 1984 American rock music mockumentary comedy film directed, co-written, scored by, and starring Rob Reiner, and co-starring Christopher Guest, Michael McKean and Harry Shearer.  The film portrays the fictional British heavy metal band Spinal Tap.  The film satirizes the wild personal behavior and musical pretensions of hard rock and heavy metal bands, as well as the hagiographic tendencies of rock documentaries of the time.  The three main members of Spinal Tap—David St. Hubbins, Derek Smalls and Nigel Tufnel—are played by actors McKean, Shearer, and Guest, respectively.  The three actors play their musical instruments and speak with mock English accents throughout the movie.  Reiner appears as Marty Di Bergi, the maker of the documentary.  Other actors in the movie are Tony Hendra as group manager Ian Faith, and June Chadwick as St. Hubbins' interfering girlfriend Jeanine.  Actors Paul Shaffer, Fred Willard, Fran Drescher, Bruno Kirby, Howard Hesseman, Ed Begley, Jr., Patrick Macnee, Anjelica Huston, Vicki Blue, Dana Carvey, Billy Crystal and Linnea Quigley all play supporting roles or make cameo appearances in the movie. Harry Julius Shearer (born December 23, 1943) is an American actor, voice actor, comedian, writer, musician, author, radio host, director and producer.  He is known for his long-running roles on "The Simpsons", his work on "Saturday Night Live", the comedy band Spinal Tap and his radio program "Le Show".  Born in Los Angeles, California, Shearer began his career as a child actor.  From 1969 to 1976, Shearer was a member of The Credibility Gap, a radio comedy group.  Following the breakup of the group, Shearer co-wrote the film "Real Life" with Albert Brooks and started writing for Martin Mull's television series "Fernwood 2 Night". Robert Reiner (born March 6, 1947) is an American actor, writer, director, producer, and activist.  As an actor, Reiner first came to national prominence with the role of Michael Stivic on "All in the Family" (1971–79).  That role earned him two Emmy Awards during the 1970s.  As a director, Reiner was recognized by the Directors Guild of America (DGA) with nominations for the coming of age comedy-drama film "Stand by Me" (1986), the romantic comedy "When Harry Met Sally..." (1989), and the military courtroom drama "A Few Good Men" (1992).  He also directed the psychological horror-thriller "Misery" (1990), the romantic comedy fantasy adventure "The Princess Bride" (1987) and the heavy metal mockumentary "This Is Spinal Tap" (1984). Nigel Tufnel is a fictional character in the 1984 mockumentary film "This Is Spinal Tap".  In the film, he is the lead guitarist of the rock band Spinal Tap.  He was played by actor Christopher Guest. David Ivor St. Hubbins is a fictional character in the mockumentary film "This Is Spinal Tap" (1984).  In the film, he is the lead singer and rhythm guitarist of the mock rock band Spinal Tap.  David is played by actor Michael McKean, who improvised the role through the whole film.  McKean writes in his introduction to "This Is Spinal Tap: The Official Guide", "When I am called upon to generate copy about the mostly fictional entity called Spinal Tap, I usually do so in the mostly fictional character of David St. Hubbins..." Christopher Haden-Guest, 5th Baron Haden-Guest (born February 5, 1948), simply known as Christopher Guest, is an English-American screenwriter, composer, musician, director, actor, and comedian who holds dual British and American citizenship.  Guest is most widely known in Hollywood for having written, directed and starred in his series of comedy films shot in mock-documentary (mockumentary) style.  Many scenes and character backgrounds in Guest's films are written and directed, although actors have no rehearsal time and the ensemble improvise scenes while filming them.  The series of films began with "This Is Spinal Tap" (directed by Rob Reiner), and continued with "Waiting for Guffman", "Best In Show", "A Mighty Wind", "For Your Consideration", and "Mascots". Victory Tischler-Blue (born September 16, 1959) is an American film producer, director, writer, musician and photographer.  She was born and raised in Newport Beach, California.  Tischler-Blue began working in the entertainment industry at age 17, using the name Vicki Blue as the bassist in the American all-girl teenage rock band The Runaways.  After the demise of the band, she was cast as Cindy by director Rob Reiner in "This Is Spinal Tap".  Her film "Edgeplay" was based on Tischler-Blue's tenure in The Runaways. Frederick Charles "Fred" Willard (born September 18, 1939) is an American actor, comedian, voice actor and writer, best known for his improvisational comedy.  He is known for his roles in the Rob Reiner mockumentary film "This Is Spinal Tap", the Christopher Guest mockumentary films "Waiting for Guffman", "Best in Show", "A Mighty Wind", "For Your Consideration", and "Mascots", and the "" films.  He is an alumnus of The Second City.  He received three Emmy nominations for his recurring role on the TV series "Everybody Loves Raymond" as Robert Barone's father-in-law, Hank MacDougall.  In 2010 he received an Emmy nomination for Outstanding Guest Actor in a Comedy Series for his role on the ABC TV series "Modern Family" as Phil Dunphy's father, Frank Dunphy.
Answer: Rob Reiner