Services between Norwich and London Liverpool Street were affected in both directions from 5am onwards after the work, overseen by Network Rail, over-ran between Diss and Stowmarket, a Greater Anglia spokesman said.

The 7.30am London Liverpool Street to Norwich service was cancelled, as was the 4.55am Norwich to London Liverpool Street.

The 5.25am Norwich to London Liverpool Street service was delayed by 25 minutes, while commuters were told to expect delays of up to 30 minutes and cancellations at short notice throughout the morning.

Several services from Ipswich to London Liverpool Street were delayed by around 10 minutes.

There were also speed restrictions on the main line near London.

Meanwhile, train services between Ipswich and Cambridge were also being cancelled at short notice or delayed by up to 30 minutes.

Disruption across the region lasted until around 8am today.

The Greater Anglia spokesman apologised to passengers affected by the disruption but said a normal service is now resuming.

A Network Rail spokesman said: “We are sorry for the disruption passengers faced this morning after planned improvement work overran. Very early morning trains were affected between Norwich and London and Ipswich and Cambridge.”