Question: When was Michael Tippett's best known work composed?

Context articles: Child of Our Time
Michael Tippett
Owen Brannigan
Piano Concerto (Tippett)
Gonchigiin Birvaa
Cuthy Mede
Requiem (Anna Akhmatova)
Fantasia Concertante on a Theme of Corelli
A Child of Our Time
Bolesław Szabelski

"Not to be confused with A Child of Our Time, an oratorio (1944) by Michael Tippett"
Sir Michael Kemp Tippett {'1': ", '2': ", '3': ", '4': "} (2 January 1905 – 8 January 1998) was an English composer who rose to prominence during and immediately after the Second World War.
 In his lifetime he was sometimes ranked with his contemporary Benjamin Britten as one of the leading British composers of the 20th century.
 Among his best-known works are the oratorio "A Child of Our Time", the orchestral "Fantasia Concertante on a Theme of Corelli", and the opera "The Midsummer Marriage".
Owen Brannigan OBE (10 March 19089 May 1973) was an English bass, known in opera for buffo roles and in concert for a wide range of solo parts in music ranging from Henry Purcell to Michael Tippett.
 He is best remembered for his roles in Mozart and Britten operas and for his recordings of roles in Britten, Offenbach and Gilbert and Sullivan operas, as well as recordings of English folk songs.
British composer Michael Tippett composed his Concerto for Piano and Orchestra between 1953 and 1955 on a commission from the City of Birmingham Symphony Orchestra.
 The overall character of the work was influenced by the composer's hearing German pianist Walter Gieseking rehearse Ludwig van Beethoven's Fourth Piano Concerto in 1950.
 Its musical content, while influenced by this concerto, was also shaped largely by Tippett's opera "The Midsummer Marriage", which he had completed in 1952.
 While Tippett had conceived the work initially in the mid-1940s, he had been preoccupied in much of the intervening time with "The Midsummer Marriage".
Gonchigiin Birvaa (Mongolian: Гончигийн Бирваа ; 1916 - 2006) was a Mongolian composer.
 Described as a "prominent composer", he was said to have composed based on the memoirs of Professor P. Khorloo.
 His best known work is perhaps the ballet "Khoshuu Naadam" and the musical "Queen's Black Destiny", based on a Mongolian legend, which he composed and was written after his death by Damdin Törbat in 1983.
 He was also an author or co-author of the books "Khödöö Tiish" (1966), "Manai duu - manai tüükh" (1982), and "Zandan shoo" (1985).
 His son is Birvaagiin Mönkhbold.
Cuthy Mede is a Malawian artist.
 Lonely Planet said "possibly the best-known [Malawian] artist is Cuthy Mede – he is also actively involved in the development and promotion of Malawian art within the country and around the world."
 Cuthy Mede grew up on Likoma Island, Lake Malawi where he drew in the rough sands of the beach as a child.
 Later he studied Fine Art in Chancellor College and became a lecturer at the College in the 1970s.
 By the 1980s Mede established Gallerie Africaine in Lilongwe City Centre, the first art gallery by a local artist in Malawi.
 Mede exhibited his work widely in Malawi, becoming a successful artist selling his work to international collectors.
 Mede encouraged the work of young Malawian artists struggling to make a living selling folk art and wood carvings as street traders.
 He also brought fine art work from other Malawian artists into his Gallery.
 He was commissioned to paint a large mural decorating the City Centre.
 Mede is best known for his modern art styles: modern, futurist, cubist and pointillist, with strong local themes.
 His paintings depicted local people, historic events and current events in Malawi, Biblical references with local interpretations, indigenous religious expressions, and paintings about ideas such as Justice, Greed, Man and Machine.
 His paintings depict famine, refugees from Mozambique during the Civil War, voting and democracy, wedding celebration, spirits and possession, and the Nyau masquerade.
 Mede's less known work is realistic, including a reproduction of the Mona Lisa.
 His best known work is dominated by bright primary colors, cubist style, though his pointillist work favors ochres and softer tones in the overall effect.
 In later years Mede painted mostly in shades of blue, then white on white, the purest light.
 Mede is an evangelical Christian and his work begins with a point of light from which the rest of the painting flows, the energy from God.
 This point of light is evident in most of his paintings as a single dot, a sun or moon, or an orb.
 Best known for his paintings, Mede also produced sculptural forms such as wood figures covered in beads and pigments.
 His garden in Lilongwe was made into a work of art, in white and light, with fluorescent light tubes hanging from trees and white painted rocks lining the drive and entry.
 Mede's wife, Esther (deceased 2009), served as Principal Secretary for the Ministry of Research and Environmental Affairs in the Malawi government.
Requiem is an elegy written over three decades, between 1935 and 1961 by Anna Akhmatova.
 Akhmatova composed, worked and reworked the long sequence in secret, depicting the suffering of the common people under the Stalinist Terror.
 She carried it with her, redrafting, as she worked and lived in towns and cities across the Soviet Union.
 It was conspicuously absent from her collected works, given its explicit condemnation of the purges.
 The work in Russian finally appeared in book form in Munich in 1963, the whole work not published within the USSR until 1987.
 It would become her best known work.
Fantasia Concertante on a Theme of Corelli, also known as the Corelli Fantasia, is a work for string orchestra by the British composer Michael Tippett.
 It was commissioned by the 1953 Edinburgh Festival to commemorate the 300th anniversary of the birth of the Italian composer Arcangelo Corelli, and given its first performance on 29 August 1953, in the Usher Hall, by the BBC Symphony Orchestra conducted by Tippett.
A Child of Our Time is a secular oratorio by the British composer Michael Tippett (190598), who also wrote the libretto.
 Composed between 1939 and 1941, it was first performed at the Adelphi Theatre, London, on 19 March 1944.
 The work was inspired by events that affected Tippett profoundly: the assassination in 1938 of a German diplomat by a young Jewish refugee, and the Nazi government's reaction in the form of a violent pogrom against its Jewish population—called Kristallnacht.
 Tippett's oratorio deals with these incidents in the context of the experiences of oppressed people generally, and carries a strongly pacifist message of ultimate understanding and reconciliation.
 The text's recurrent themes of shadow and light reflect the Jungian psychoanalysis which Tippett underwent in the years immediately before writing the work.
Bolesław Szabelski (3 December 1896 in Radoryż - 27 August 1979 Katowice) was a Polish composer of modern classical music.
 While his style shifted and varied over the course of his life, he is best known for his atonal work composed during the 1950s and 1960s.