input: Kennedy is best known as the lead vocalist and guitarist of the American hard rock band Alter Bridge. The band's origins lie in late 2003 when Kennedy was contacted by former Creed guitarist Mark Tremonti, who was interested in having Kennedy lay down vocal tracks for some songs he had recently written. Tremonti and drummer Scott Phillips had reunited with former bassist Brian Marshall who had left Creed in 2000 to form a new band. Alter Bridge, taking its name from an actual bridge that used to be located near Tremonti's home in Detroit, was officially formed in January 2004. Coinciding with the official announcement of Alter Bridge's formation was an announcement regarding their debut album, One Day Remains, along with the release of that album's lead single, "Open Your Eyes." One Day Remains was released in 2004 on Wind-up Records. It received generally mixed to negative reviews and was certified Gold by the RIAA. Two other singles, "Find the Real" and "Broken Wings" were released. One Day Remains was the only album by a band with Kennedy as an official member that does not feature his guitar playing, before his 2014 album "World On Fire" as a part of Slash featuring Myles Kennedy and the Conspirators.  Following a successful tour in support of the album, Alter Bridge announced plans for a second release. The album, Blackbird, was released in 2007 on Universal Republic to mostly positive reviews. Unlike One Day Remains, which was largely written by Tremonti, Blackbird featured Kennedy's guitar playing as well as more of his songwriting contributions. Alter Bridge toured in support of Blackbird throughout 2007 and 2008, recording a concert film titled Live from Amsterdam and releasing it in 2009 via Amazon.com. It would later be released in stores in early 2011 after several delays.  Alter Bridge took a temporary break in early 2009 with its members working on other projects, but the band continued writing music throughout the year. The band regrouped later that year to begin work on their third album, AB III, which was released in 2010 on Roadrunner Records worldwide, except for North America where the album was self-released on Alter Bridge Recordings via EMI. For the album, Kennedy chose to write lyrics based on his own personal experiences with faith and believing. As such, it is lyrically the band's darkest album, with Kennedy calling it the most personal album he had made since The Mayfield Four's Second Skin. AB III has received critical acclaim. A second concert film, Live at Wembley, was released on March 26, 2012. The band reunited in late 2012 and recorded from April to July 2013 their fourth album titled Fortress, which was released on September 30, 2013. The band reconvened in January 2016 and, through that July, recorded their fifth album The Last Hero, which was released on October 7, 2016.  Having joined Alter Bridge primarily as lead vocalist, Kennedy began to play rhythm guitar during live performances following the release of One Day Remains. He has since played rhythm guitar on the band's subsequent studio releases, and also played lead tracks on a number of songs and during live performances.

Answer this question "Why was he contacted by Mark?"
output: who was interested in having Kennedy lay down vocal tracks for some songs he had recently written.

Question: Kwame Nkrumah PC (21 September 1909 - 27 April 1972) was a Ghanaian politician and revolutionary. He was the first prime minister and president of Ghana, having led it to independence from Britain in 1957. An influential advocate of Pan-Africanism, Nkrumah was a founding member of the Organization of African Unity and winner of the Lenin Peace Prize in 1962. After twelve years abroad pursuing higher education, developing his political philosophy, and organizing with other diasporic pan-Africanists, Nkrumah returned to Gold Coast to begin his political career as an advocate of national independence.

Nkrumah returned to London in May 1945 and enrolled at the London School of Economics as a PhD candidate in anthropology. He withdrew after one term and the next year enrolled at University College, with the intent to write a philosophy dissertation on "Knowledge and Logical Positivism". His supervisor, A. J. Ayer, declined to rate Nkrumah as a "first-class philosopher", saying, "I liked him and enjoyed talking to him but he did not seem to me to have an analytical mind. He wanted answers too quickly. I think part of the trouble may have been that he wasn't concentrating very hard on his thesis. It was a way of marking time until the opportunity came for him to return to Ghana." Finally, Nkrumah enrolled in, but did not complete, a study in law at Gray's Inn.  Nkrumah spent his time on political organising. He and Padmore were among the principal organizers, and co-treasurers, of the Fifth Pan-African Congress in Manchester (15-19 October 1945). The Congress elaborated a strategy for supplanting colonialism with African socialism. They agreed to pursue a federal United States of Africa, with interlocking regional organizations, governing through separate states of limited sovereignty. They planned to pursue a new African culture without tribalism, democratic within a socialist or communist system, synthesizing traditional aspects with modern thinking, and for this to be achieved by nonviolent means if possible. Among those who attended the congress was the venerable W. E. B. Dubois along with some who later took leading roles in leading their nations to independence, including Hastings Banda of Nyasaland (which became Malawi), Jomo Kenyatta of Kenya, Obafemi Awolowo of Nigeria, and C. L. R. James.  The congress sought to establish ongoing African activism in Britain in conjunction with the West African National Secretariat (WANS) to work towards the decolonization of Africa. Nkrumah became the secretary of WANS. In addition to seeking to organise Africans to gain their nations' freedom, Nkrumah sought to succor the many West African seamen who had been stranded, destitute, in London at the end of the war, and established a Coloured Workers Association to empower and succor them. The U.S. State Department and MI5 watched Nkrumah and the WANS, focusing on their links with Communism. Nkrumah and Padmore established a group called The Circle to lead the way to West African independence and unity; the group aimed to create a Union of African Socialist Republics. A document from The Circle, setting forth that goal, was found on Nkrumah upon his arrest in Accra in 1948, and was used against him by the British authorities.

Using a quote from the above article, answer the following question: when did he go to London?
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Answer:
Nkrumah returned to London in May 1945 and enrolled at the London School of Economics as a PhD candidate in anthropology.