On April 4 1968 the civil rights activist Martin Luther King was shot dead on the balcony of a motel in Memphis, Tennessee.

King's tireless efforts on behalf of the US civil rights movement shaped America and the high demand for collectibles related with the Nobel Peace Prize winner is testament to his impact on the world.

A signed copy of King's 1961 book Stride Toward Freedom sold recently for £6,000 while in 2005, a 1968 letter from King to tennis star Arthur Ashe, thanking him for a recent speech Ashe had made, sold for £6,000. In the letter King applauds Ashe for his "expression of support and solidarity in the fight for justice, freedom and dignity for all people in this country".

Savvy investors may be interested in purchasing a rare King signed programme, which can currently be obtained without the uncertainty of bidding at an auction.

King's campaign of peaceful protest was not always followed by his contemporaries. Items associated with Michael X, the Trinidadian black power activist, and the first black man to be convicted under the Race Relations Act for inciting racial hatred, are also highly coveted, with signed photographs proving popular.

Martin Luther King died aged just 39

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