Within a year of his arrival, he was taking on the roles of Special Projects Coordinator at the Greater London Council (GLC), and Chair of the African Refugees Housing Action Group, and later Operations Manager of the Notting Hill Carnival.

[9] As Special Projects Coordinator of the Ethnic Minorities Unit at the GLC, Addai-Sebo was instrumental in inaugurating the UK's annual Black History Month, first celebrated in 1987.

Jesse Jackson, Angela Davis, Winnie Mandela, Marcus Garvey Jr., Sally Mugabe, Graca Machel, John Henrik Clarke, Yosef Ben-Jochannan, Burning Spear, Ray Charles, Max Roach, Hugh Masekela and many more came to London between 1985 and 1988 at the invitation of the GLC to support the anti-racist and anti-apartheid campaigns.

"[10] The lectures would be compiled into the book Our Story: A Handbook of African History and Contemporary Issues (London Strategic Policy Unit, 1988), which Addai-Sebo edited with Ansel Wong.

[10] "Our original goal was to first create an enabling cultural space in the UK celebratory calendar and after public acceptance and recognition extend the observance of October as a month to a Black History Season.

[12][13] Addai-Sebo has noted: "Although I initiated the idea, making Black History Month was a collective effort, and it could not have been achieved without the London Strategic Policy Unit, an organisation established after the Thatcher government abolished the GLC in 1986.