It was one of the most turbulent periods in US history, the impact of which is still being felt to this day. It is therefore unsurprising that the market for civil rights collectibles is strong, with memorabilia and historical documents commanding high sums at auction.

For example, a signed copy of Martin Luther King's 1961 book Stride Toward Freedom recently sold for £6,000. There are other opportunities for investors to get their hands on signed items by the man regarded as one of the 20^th century's most influential figures, such as this rare programme.

A diary Malcolm X was carrying the day he was assassinated in February 1965 was pulled from auction in 2002 following a dispute of ownership. It had been expected to sell for $50,000.

Martin Luther King and Malcolm X

In the early 1970s, John Lennon and Yoko Ono donated a bag of their hair to Black House, a north London black power group. Collecting celebrities' hair continues to be popular today, with sites such as A Small Piece of History doing a brisk trade.

Black House was closely linked with Michael X, the Trinidadian black power activist, who was the first black man to be convicted under the Race Relations Act for inciting racial hatred. Signed photographs of the man are highly prized among collectors.