What is the first name of the person whose predominant works of the 1950s were his three last symphonies?  Answer the above question based on the context below:  In February 1953 Vaughan Williams and Ursula were married. He left the Dorking house and they took a lease of 10 Hanover Terrace, Regent's Park, London. It was the year of Queen Elizabeth II's coronation; Vaughan Williams's contribution was an arrangement of the Old Hundredth psalm tune, and a new setting of "O taste and see" from Psalm 34, performed at the service in Westminster Abbey. Having returned to live in London, Vaughan Williams, with Ursula's encouragement, became much more active socially and in pro bono publico activities. He was a leading figure in the Society for the Promotion of New Music, and in 1954 he set up and endowed the Vaughan Williams Trust to support young composers and promote new or neglected music. He and his wife travelled extensively in Europe, and in 1954 he visited the US once again, having been invited to lecture at Cornell and other universities and to conduct. He received an enthusiastic welcome from large audiences, and was overwhelmed at the warmth of his reception. Kennedy describes it as "like a musical state occasion".Of Vaughan Williams's works from the 1950s, Grove makes particular mention of Three Shakespeare Songs (1951) for unaccompanied chorus, the Christmas cantata Hodie (1953–1954), the Violin Sonata, and, most particularly, the Ten Blake Songs (1957) for voice and oboe, "a masterpiece of economy and precision". Unfinished works from the decade were a cello concerto and a new opera, Thomas the Rhymer. The predominant works of the 1950s were his three last symphonies. The seventh—officially unnumbered, and titled Sinfonia antartica—divided opinion; the score is a reworking of music Vaughan Williams had written for the 1948 film Scott of the Antarctic, and some critics thought it not truly symphonic. The Eighth, though wistful in parts, is predominantly lighthearted in tone; it was received enthusiastically at its premiere in 1956, given by the Hallé Orchestra under the dedicatee, Sir John Barbirolli. The Ninth, premiered at a Royal Philharmonic Society concert...
The answer to this question is:
Vaughan