The former manager at the Trackwork depot in West-bury has admitted stealing thousands of pounds worth of scrap railway lines from work.
Martin Wrighthouse was one of six men who were due to stand trial before a judge at Swindon crown court on Monday.
But before a jury could be sworn on the first morning of the three weeks set aside for the case, the 51-year-old and haulier Melvyn Bownes, 50, each admitted theft.
And once they had changed their pleas to guilty, prosecutors dropped the charges against the four other men in the dock alongside them.
Iain Bryers, 45, Craig Chadwick, 44, Stephen Page, 54, and Daniel Bownes, 21, all had formal not guilty verdicts entered in their cases.
Wrighthouse, formerly of Primrose Place, Westbury, but now living in Cheshire and Melvyn Bownes, of Worksop, Nottinghamshire, admitted taking lengths of track, which belonged to Network Rail and were worth up to £3,990, from the depot on December 22, 2011.
The pair had also been accused of staging a cover up by causing a false order form.But prosecutors said they would not seek a trial on the charge of perverting the course of justice and asked for the count to lie on file.
Judge Douglas Field adjourned the case to April 12, and cleared Bryers, of Fell Road, Westbury, Page, of Southampton, and Daniel Bownes, of Worksop, Notts, of theft; and Chadwick, of Bridge Court, Westbury, of perverting the course of justice.
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