Question: The man who composed the music for Thomas and the King was the Boston Pops' principal conductor during what years?

<P0-S0> Thomas and the King is a stage musical with music by John Williams, lyrics by James Harbert, and a book by Edward Anhalt. <P0-S1>  It is based on the story of Thomas Becket and Henry II of England, and set in 12th century England. <P0-S2>  It opened at Her Majesty's Theatre London, 16 October 1975 to poor reviews and failed to make it to Broadway. <P0-S3>  The set was designed by Tim Goodchild. <P0-S4>  The musical was directed and choreographed by Norman Maen. <P0-S5>  The cast included James Smilie, Richard Johnson, Caroline Villiers, Martin McEvoy, and Dilys Hamlett. <SEP> <P1-S0> "Sleigh Ride" is a popular light orchestral Christmas music standard composed by Leroy Anderson. <P1-S1>  The composer had the original idea for the piece during a heat wave in July 1946 and finished the work in February 1948. <P1-S2>  It was originally an instrumental piece; the lyrics, about someone asking another to join them for a ride in a sleigh, were written by Mitchell Parish in 1950. <P1-S3>  The orchestral version was first recorded in 1949 by Arthur Fiedler and the Boston Pops Orchestra. <P1-S4>  Sleigh Ride was a hit record on RCA Victor Red Seal 49-0515 (45 rpm) / 10-1484 (78 rpm), and has become a signature song for the orchestra. <P1-S5>  The 45 rpm version was originally issued on red vinyl. <P1-S6>  The Pops has also recorded the song with John Williams, their conductor from 1979 to 1995, and Keith Lockhart, their current conductor. <SEP> <P2-S0> John Towner Williams (born February 8, 1932) is an American composer, conductor, and pianist. <P2-S1>  With a career spanning over six decades, he has composed some of the most popular and recognizable film scores in cinematic history, including "Jaws", the "Star Wars" series, "Close Encounters of the Third Kind", "Superman", "E.T. the Extra-Terrestrial", the "Indiana Jones" series, the first two "Home Alone" films, the first two "Jurassic Park" films, "Schindler's List", and the first three "Harry Potter" films. <P2-S2>  Williams has been associated with director Steven Spielberg since 1974, composing music for all but three of his feature films. <P2-S3>  Other notable works by Williams include theme music for the Olympic Games, "NBC Sunday Night Football", "The Mission" theme used by NBC News, the television series "Lost in Space" and "Land of the Giants", and the incidental music for the first season of "Gilligan's Island". <P2-S4>  Williams has also composed numerous classical concertos and other works for orchestral ensembles and solo instruments. <P2-S5>  From 1980 to 1993, he served as the Boston Pops' principal conductor, and is now the orchestra's laureate conductor. <SEP> <P3-S0> A Trumpeter's Lullaby is a short composition for solo trumpet and orchestra, written by American composer Leroy Anderson in 1949. <P3-S1>  The two and a half minute piece was premiered on May 9, 1950, by the Boston Pops Orchestra with Arthur Fiedler conducting and French-born American Roger Voisin as trumpet soloist. <P3-S2>  It was composed at the request of Voisin, who was principal trumpeter of the Boston Pops Orchestra at the time. <P3-S3>  It was first recorded on June 18, 1950, with Fiedler conducting Roger Voisin and the Boston Pops. <P3-S4>  Three months later it was recorded with Anderson himself conducting and James F. Burke as trumpet soloist. <P3-S5>  The first stereo recording was made in October 1956 with Frederick Fennell conducting the Eastman-Rochester Pops Orchestra, recorded in one take without rehearsal. <P3-S6>  The (uncredited) soloist was Sidney Mear.