The damage meant reduced services and delays

Train operator One said local services to Cambridge, Sheringham, Lowestoft, and Great Yarmouth were also affected.

Cables at Newton Flotman, between Norwich and Diss, were cut overnight.

A spokesman for train operator One said by late afternoon travellers were still facing 20-minute delays. Network Rail engineers were repairing the cables.

'Serious sabotage'

Network Rail spokesman Jon Wiseman said the it was the most serious sabotage he had come across and it had been very disruptive.

Earlier One spokesman Peter Meades said: "We are running services, but it means Network Rail have had to put in place some temporary signalling arrangements.

"This is not ideal because it means the trains won't be running at their normal speed and it also means we'll be thinning out the service in order just to keep trains moving."

He said passengers should be prepared for delays, particularly between Norwich, Diss and Stowmarket.

British Transport Police, who are investigating the vandalism, said the cables were cut late on Thursday night or in the early hours of Friday at two separate locations in Newton Flotman.