NEW trains whose launch on London Overground has been delayed for a year by technical problems are set to carry passengers for the first time.

Class 710 Bombardier Aventra trains are expected to enter service today between Gospel Oak and Barking, and the arrival of the first two units will allow the frequency of trains on the route to be increased. Another six are expected soon.

The line itself was electrified a couple of years ago, but the Class 710s were paralysed by a series of software problems. It had been reported that more than 20 versions of the safety-critical Train Management System had to be tried by Bombardier.

The former Class 172 diesel sets on the line were withdrawn for service with West Midlands Trains a few months ago, because Transport for London had been expecting the new trains by June 2018 at the latest and so allowed the diesel leases to expire.

When the other trains have arrived and are running every 15 minutes the capacity of the line will be almost doubled, because the new electric units are twice the length of the former diesels and can carry 700 people.

The gap between old and new rolling stock meant that services on the line had to be reduced to skeleton level this year, using three Class 378 sets which had been ‘borrowed’ from other London Overground routes. These were all that could be spared, but the frequency on the line was reduced to half-hourly as a result.

Transport for London says it hopes to restore the 15-minute frequency later this summer, and that passengers on the line will be offered free travel throughout September, paid for by Bombardier.

Deputy Mayor for transport Heidi Alexander said: ‘When I wrote to Bombardier earlier this year I made our frustrations at the delay clear, so I am pleased that the first two new trains will be in operation. The full timetable will be restored as soon as possible. The month’s free travel, which was requested by the Mayor, is a well-deserved thank you to passengers for their patience.’

TfL director of rail Jonathan Fox added: ‘It is good news that these London Overground trains are finally here and will make their inaugural passenger run this week. This is the first step in returning to the regular timetable and delivering the much-needed capacity on the Gospel Oak to Barking line. We know this has been a long time coming and we will be offering a month of free travel for customers. I am pleased we will now make a real difference to their journeys.’

The full Aventra order is for 54 four-car trains. Apart from the eight allocated to Gospel Oak-Barking, the rest will work services between Liverpool Street, Cheshunt, Chingford and Enfield Town, and also between Euston and Watford Junction.

The Gospel Oak-Barking line will grow in 2021, when an extension to Barking Riverside is opened.