Rail passengers travelling between Norwich and Thetford faced delays after a signalling fault caused lines to become blocked.
A fault with the system between Thetford and Wymondham caused headaches for passengers during rush hour.
The fault is believed to have been caused by an external electrical supply problem.
Network Rail engineers installed a generator to restore the signalling.
The issue began around 3pm and Greater Anglia reported that services resumed just after 6pm.
However, disruption on the Norwich to Cambridge line continued until after 7pm.
A limited rail replacement bus service was put on between Ely/Thetford and Norwich to transport affected passengers.
A spokesman for Greater Anglia apologised for disruption to passengers' travel plans.
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