New trains that were sitting idle for months will finally start to be used between Welwyn Hatfield and London.
The new 717 specification trains were supposed to be gradually introduced from January, but were delayed due to concerns about driver safety.
Welwyn Hatfield MP Grant Shapps, who has been in close contact with executives at Govia Thameslink Railway, said: "The new trains are a huge improvement on the last fleet, which were some of the oldest in Britain.
"For months my constituents and I have suffered with overcrowding while the 717s have been sitting unused in the sidings. Their full introduction is certainly welcome news."
A spokesperson for Govia said: "We are introducing two new trains this week and one next week, which will bring the total to eight in service. The remainder will be phased in over the coming months.
"The new trains will run on routes between Welwyn Garden City and Moorgate, and between Hertford North and Moorgate; and at weekends also between Stevenage and Moorgate."
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