Commuters faced long queues on station platforms after a signal fault on one of the country's busiest rail routes caused delays.
The problem with the signalling system between Alexandra Palace and New Barnet in north London caused disruption to East Coast Main Line services.
Network Rail and First Capital Connect apologised for the disruption.
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Calls are being made for East Coast Main Line trains to remain in public ownership.
The service, which runs through Stevenage and Peterborough, has reported a return of more than £200 million since it was re-nationalised when the previous private operator handed back the franchise.
Green Party politicians are planning to hand in a petition containing 23,000 signatures calling for the service not to be franchised back to the private sector
The Government's confirmed today that the East Coast main line, which runs through Peterborough and Stevenage, will be put out to tender after four years in public ownership. Not everyone's happy about it. Watch Elodie Harper's report.
The Greater Anglia rail franchise covering most passenger train services in Norfolk, Suffolk and Essex is to be extended by more than two years.
The deal with Dutch operator Abellio, which began in February last year, was due to expire next July, to be replaced by a long-term franchise running for around 15 years.
The East Coast main line, which runs through Stevenage and Peterborough, is to be re-privatised under plans announced by the Government.
The franchise has in the past been given up twice by the private sector, with the line being run by the Department for Transport since the end of 2009.
A bidding competition has now started with a new operator expected to be in place by February 2015.
A transport union boss has described the Government's announcement to privatise the East Coast main line as "profiteering".
General secretary of the RMT Bob Crow said: "Despite wasting hundreds of millions of pounds of taxpayers' money on the franchising circus, and instead of learning the lessons of the privatisation disasters on the East and West Coast main lines and across the rest of the network,
the Government has this morning given the green light to a whole new wave of profiteering that will have the train companies laughing all the way to the bank."
The Transport Secretary Patrick McLoughlin has said privatising the East Coast main line would put passengers "in the driving seat".
Mr McLoughlin said: "This programme is a major step in delivering tangible improvements to services, providing long-term certainty to the market and supporting our huge programme of rail investment.
"Above all, in future franchise competitions we are placing passengers in the driving seat by ensuring that their views and satisfaction levels are taken into account when deciding which companies run our railway services."
By next year passengers can expect trains to be less packed. A new flyover at Hitchin will carry trains from London to Cambridge over the main line, relieving a key bottleneck.
New platforms planned for Peterborough should increase capacity and reduce congestion there.
From 2014 new trains through the Intercity Express Programme will provide more seats, and £240m will be invested in key pinch points on the East Coast main line including Peterborough.
The East Coast main line that runs through Stevenage and Peterborough will be one of the first in the country to get new trains after the government confirmed a £4.5bn deal has been agreed to build new rolling stock.