A signed letter from Muhammad Ali to Nelson Mandela is to cross the block at Henry Aldridge & Son.
It dates to April 13, 1993 and offers his condolences following the assassination of Chris Hani, head of the armed wing of the African National Congress (ANC), by white supremacist Janusz Walus.
Muhammad Ali gives Nelson Mandela his condolences after the killing of the ANC's Chris Hani
It later transpired that Walus had links to senior figures in the ruling pro-apartheid South African Conservative Party.
Hani's death led to riots and a personal appeal for calm from Mandela himself, who said: "Now is the time for all South Africans to stand together against those who, from any quarter, wish to destroy what Chris Hani gave his life for - the freedom of all of us."
A year later the first free and fair elections were held in the country, which Mandela and the ANC won with a landslide 62.6% of the vote.
Ali dictated the letter to the secretary of a hotel in Durban, South Africa - who explains in a letter of provenance: "Due to my nervous excitement about typing a letter of such historical importance I misspelt the name Muhammad replacing the last "a" with an "e".
"The letter was taken to Muhammad Ali and duly signed before someone noticed the error and returned it to me. I typed it again but kept the incorrect copy for posterity."
The letter concerns two of the most important figures of the 20th century, both of whom passed away recently, a factor that could see it sell for well beyond its £8,000 ($10,168) estimate on December 17.