The Government has agreed to buy new trains worth £155million to improve the rail service to Stansted airport.

Thirty new trains will be built by Bombardier in Derby to replace the existing class 317 trains which are nearly 30 years old and run services from London Liverpool Street to Stansted airport and Cambridge.

The new four-car Electrostar trains will be delivered in two years time.

"We are extremely pleased that our Electrostar trains have been chosen to welcome visitors arriving into the UK via Stansted airport," said Colin Walton of Bombardier.

The 317 trains were originally used to run trains from St Pancras to Bedford when the line was electrified in the 1980s.

In future the 317s will allow longer trains to be run on West Anglia services in East London and Hertfordshire.

Services on the Great Eastern main line from Liverpool Street to Chelmsford, Colchester and Ipswich will also be boosted by the transfer of 17 class 321 trains from London Midland which is now taking delivery of a new fleet of German-built Siemens Desiro trains.

The transfer of the "refreshed" 321 trains will start in December and take two years to complete.

Jonathan Denby of National Express East Anglia said: "This is fantastic news – the culmination of two years hard work by many people at NXEA."

Transport Secretary Geoff Hoon said: "This will be of major benefit to passengers in reducing overcrowding.

"Bombardier's success will help safeguard UK manufacturing jobs and the expansion of the fleet will create job opportunities with NXEA."

The Government says the new build and transfer programme will create 11,000 extra seats on train services into Liverpool Street – a 17% increase in the NXEA fleet.

The new trains are designed for speeds of up to 100mph and are equipped with large luggage racks, air conditioning, CCTV, WiFi and regenerative braking.

Bombardier will maintain the new trains at Ilford, east London, but Clacton depot in Essex is being brought back into use as a maintenance facility to cope with the enlarged fleet and NXEA is expected to take on 100 extra staff.

Network Rail will lengthen station platforms to accommodate longer trains.

Information from the department for Transport, NXEA and Bombardier.