Engineers at Greater Anglia and Network Rail have still not found the cause of the signalling problems that have emerged since the introduction of new Stadler trains on many routes.

But they have been able to restore a near-normal service between Ipswich and Cambridge by running it with just old diesel trains. Greater Anglia still has nine of these trains in its fleet before they are transferred to other operators in the spring of 2020.

Services between Ipswich and Peterborough are still suspended and buses continue to replace trains on the Felixstowe branch. An emergency timetable has been introduced on the East Suffolk Line between Ipswich and Lowestoft.

While the focus is firmly on the rural services, Greater Anglia is also preparing its new Intercity trains running from Ipswich and Norwich to London. They are mechanically very similar to the bimode trains - but without the diesel power car in the middle.

They were due to start being introduced now and are due to have taken over all Intercity services by the end of March.

But there are growing doubts about whether the first new trains will be in service before the end of the year.

And it is understood that Greater Anglia would be prepared to hold back some of their existing Intercity trains in reserve after the new trains are introduced in case teething troubles emerge.

One complication could be that the Class 90 electric locomotives currently used are due to be transferred to freight company Freightliner at the end of March - however it is not unusual for train companies to sub-lease locomotives off other operators for short-term use to cover shortages.

Meanwhile a Greater Anglia spokesman said the company's engineers were continuing to work with Network Rail colleagues to try to resolve the issues.

He said: "We haven't solved the problems yet, but obviously we hope to come up with solutions as soon as possible. We are looking at many possible solutions."

The company remains hopeful that solutions will be found within a reasonable time - and will be hoping that any solutions learned with the bimodes would be able to be implemented with the Intercity trains when they start to come into service.