Rail union RMT say there could be "another Hatfield" after releasing a picture of a six inch gap in the East Coast Mainline track near Selby.
An investigation's been launched by the Rail Accident Investigation Branch after the picture was taken last Friday at Hambleton South junction, and the union says it is due to staffing cuts.
An investigation found the Hatfield crash - which killed four people when a train travelling from London to Leeds derailed in 2000- was caused by "critical cracks" on the track.
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Most escaping a frost overnight with cloudier skies and patchy rain. Turning colder on Monday stronger northerly winds, rain and hill snow.
By the end of Monday a cold northerly wind, widespread frost and risk of wintry showers
Flying Scotsman travelled alongside three modern trains to celebrate the "past, present and future" of Britain's railway this morning.