A thief who used a crane and five lorries to steal 171 tonnes of railway track from the side of the main line from Bristol Parkway to London could have caused a "serious rail crash", say police (links below.)
http://www.rmtbristol.org.uk/2008/06/rail_line_theft_could_have_cau.html#more

http://news.bbc.co.uk/1/hi/wales/7434084.stm

Anthony Porretta, 53, masterminded the theft of the 40ft lengths of steel track, worth £22,308, from Acton Turville, near Chipping Sodbury, during engineering works.