Network Rail has awarded the contract for the design and build of the Bermondsey diveunder – a crucial component of the final phase of the £6bn Thameslink programme – to Skanska.

With a projected completion date of spring 2017, the diveunder will create a major grade-separated junction on the eastern approach to London Bridge station, allowing the Thameslink lines to cross the Kent lines unimpeded on their approach to the station and increasing the number of trains which can serve London Bridge.

The diveunder will be formed by a series of new structures constructed along the line of existing operational railway viaducts, reusing existing structures wherever possible to reduce disruption and waste.

Skanska has previously been involved in the Thameslink programme, building the new Borough viaduct to the north of the station which will allow more trains to continue their journey into and across the capital.

Andy Gent, Network Rail project director, said: “The work at Bermondsey is crucial to the Thameslink programme and it’s essential we do this efficiently and with minimal disruption to passengers. We have an excellent track record of delivering infrastructure improvements with Skanska and we look forward to working with them again to improve the railway for passengers in London.”

The first stage of the Thameslink programme will conclude this year and has seen major station redevelopments at Farringdon and Blackfriars and the introduction of longer, 12-carriage trains on the Thameslink route from Bedford to Brighton.

The final stage of the programme centres on the transformation of London Bridge station and the surrounding railway. Work is due to start in 2013 and should be completed in 2018. At this time the frequency of trains through the Thameslink route’s central London ‘core’ will increase from 16 to 24 per hour, providing a much needed capacity boost.