The General Secretary of the RMT Union is expected to call for the creation of a "new party of labour" at today's Durham Miners' Gala.
Speaking in advance of the Gala, RMT General Secretary Bob Crow said: "There is a whole world of opportunity outside the constraints of the Labour Party and RMT would urge them to embrace it and join us in this new political project."
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Sandiford, a former legal secretary originally from Redcar, was convicted of drug smuggling offences and sentenced to death in 2013.
Durham Crown Court heard that one of the male victims suffered a triple-fractured jaw, while left lying in the gutter, unconscious.