In 1992, Williamson launched a literary magazine called Rebel Inc[2] and through its pages, was one of the first publishers of such Scottish writers as Irvine Welsh, Laura Hird, Alan Warner, and Toni Davidson.
In 1996 Williamson joined forces with Edinburgh-based Canongate Books to create the Rebel Inc imprint[3] which, in the following five years, published almost sixty titles, mixing Scottish fiction with the international counter-culture and the politics of dissent.
In 2003, Williamson became the first person to be physically ejected by the police from the Scottish Parliament when he made an anti-war protest wearing a George Bush mask.
[8] In August 2006, in the aftermath of Tommy Sheridan's libel case against the News of the World, Williamson parted company with the Scottish Socialist Party.
Since acrimoniously parting company with Canongate Books, Williamson has worked as a newspaper columnist and cultural commentator, regularly appearing in print and on television and radio.