RMT are protesting outside Preston Crown Court ahead of Network Rail's sentencing over the Grayrigg crash in 2007. They face an unlimited fine.
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The two grenades were on board a fishing boat heading for Stranraer harbour.
Storm Doris is set to bring wet, windy and wintry weather to the region.
Carl Hodgson, who lives in the town, was sentenced to three years and six months behind bars at Manchester Crown Court today.