The new franchise running rail services between King's Lynn and London experienced a minor setback when two trains broke down on its first day in charge.

The 8.55am Lynn to London service was delayed for 18 minutes after encountering problems at Ely.

Govia Thameslink Railway, which has taken over the new Thameslink, Southern and Great Northern franchise, said the incident caused a 'minor delay'. Earlier, passengers in Hertfordshire also faced delays when an early morning commuter service broke down and had to be replaced.

A spokesman for Govia Thameslink said: 'We would like to apologise to our passengers for disruption they may have faced earlier today.

'A train – the 6.43 from Welwyn Garden City – broke down in Moorgate at 7.30.

'Services were either diverted into King's Cross or the remaining platform at Moorgate with delays of up to 20 minutes. We arranged for our passengers to be able to use their tickets on London Underground. Services returned to normal at 9.15.'

Govia is pledging major new investment in the network, including a fleet of new, faster trains with 50pc more capacity, with 10,000 extra seats every weekday into central London during the morning peak by the end of 2018. Millions of pounds will also be invested in improving stations and staffing, with new targets to improve train punctuality and cleanliness, while web, smartphone and tablet apps will be developed for passengers.

Improvements due in the lifetime of the new franchise include improvements to a junction near Ely which will allow trains to run half-hourly between Lynn and London.

The seven-year franchise is the largest ever let in terms of passenger numbers with around 273m passenger journeys annually.

It replaces the previous Thameslink and Great Northern franchise, operated as First Capital Connect. The South Central Franchise will also be included when it expires in July 2015.

Rail Minister Claire Perry said: 'The new TSGN will be at the forefront of the massive investment we are making in the rail network in London and the South East.

'Passengers can look forward to new trains, more seats, improved stations and better services and today marks the very start of that journey.'

Govia Thameslink Railway chief executive Charles Horton said: 'There's no underestimating the challenge of the task ahead but I am confident that we have the people and the plans in place to make a real difference to the service we give our passengers.' Previous franchise holder First Capital Connect gave Lynn station a retro makeover before its tenure ended.