ENGINEERING work will affect the railway line which runs through Times Territory tonight (Thursday).
A First Capital Connect spokesman said track improvements and maintenance would start at 11.55pm.
A replacement bus service will operate between Alexandra Palace and Stevenage.
Our affected stations are Potters Bar, Brookmans Park, Welham Green, Hatfield, WGC, Welwyn North and Knebworth.
Passengers should allow extra time for journeys, the spokesman added.
Normal service will resume at 5.30am tomorrow morning (Friday).
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