How we did it: Teamwork trust speeds station's terminal role

Ben Willis, Planning, 29 August 2008

Background: As part of High Speed 1, the Channel Tunnel Rail Link extension into London, William Barlow's 1863 station was reborn as a modern-day international terminal able to accommodate Eurostar trains.

Who is behind it? London and Continental Railways, architects Foster & Partners, English Heritage, London Borough of Camden, engineering consortium Rail Link Engineering comprising Arup, Bechtel, Halcrow and Systra.

Project aims: Extension and refurbishment of St Pancras station as London's Eurostar terminal.

Skills involved: Architecture, structural engineering, conservation, partnership working.

In 1996, parliament passed the Channel Tunnel Rail Link Act, paving the way for a high-speed continental rail link into central London. As part of this, the UK's Eurostar terminal was moved from its original home in Waterloo to St Pancras station in north London.

Years of neglect had left the grade I listed Victorian building in a state of general decay, but the high quality of the original construction meant that much of its valuable historic fabric was still intact. Conservation of these features became an overriding objective of the refurbishment.

This led to some early tensions over the project's direction. "The act's planning regime gave us quite a lot of scope to do things operationally for the railway, but it made other parties nervous that we would use the powers in an unsympathetic way. That was particularly true with English Heritage. It was concerned that somehow the grade 1 listed building would suffer," explains London & Continental Railways (LCR) managing director Stephen Jordan.

To allay these concerns early on, LCR invited English Heritage and officers from the London Borough of Camden to regular meetings with the project architects and engineers where their thinking on the design principles was laid out.

This collaborative approach led to a major breakthrough with the design. In the original concept, the undercroft beneath the train deck was effectively dead space, with the new amenities and access to the platforms set on raised mezzanine walkways in the train shed. "This was not very good for the lovely great train shed and neither was it an efficient use of space," says Jordan.

Instead, the architects and engineers came up with a solution to cut holes in the deck to unite the upper and lower levels of the station. All amenities were located in the undercroft with access to the platforms provided by a series of escalators.

A major sticking point on the proposal was that it would involve the loss of some of the station's cast iron columns, a central element of its listed status. But because of the relationship built up through the meetings, Camden and English Heritage were prepared to sacrifice columns that everyone had thought were sacrosanct. "It was a positive compromise that could only happen once we had established trust," maintains Jordan.

Beyond negotiations on conservation implications, another key challenge for the team lay in keeping the station operational throughout the refurbishment programme. "The engineers came up with the idea of building the platform deck extension one half at a time, moving services from side to side as the work was completed," Jordan recalls. "That allowed us to complete the project in a staged way. We had two interim stations, effectively."

The condition of certain parts of the building also caused headaches. The roof had been poorly repaired after sustaining bomb damage in the Second World War. "One of the objectives of the refurbishment was to bring the roof and glazing back to its original quality," Jordan says. A system of ridge-and-furrow glazing that followed the original design involved more than 14,000 individual panels to give a total glazed area of 10,000m2 - the equivalent of two football pitches.