By early 2004, the eastern side of the extended train shed was complete, and the Barlow train shed was closed to trains.
From 12 April 2004, Midland Mainline trains terminated at an interim station occupying the eastern part of the extension immediately adjacent to the entrance.

As part of the construction of the western side of the new train shed that now began, an underground "box" was constructed to house new platforms for Thameslink, which at this point ran partially under the extended station.
In order for this to happen, the existing Thameslink tunnels between Kentish Town and King's Cross Thameslink were closed between 11 September 2004 and 15 May 2005 while the works were carried out.
Thameslink services from the north terminated in the same platforms as the Midland Main Line trains, while services from the south terminated at King's Cross Thameslink.

When the lines were re-opened, the new station box was still only a bare concrete shell and could not take passengers.
Thameslink trains reverted to their previous route but ran through the station box without stopping.
The budget for the Channel Tunnel Rail Link works did not include work on the fitting out of the station, as these works had originally been part of the separate Thameslink 2000 works programme.
 Despite lobbying by rail operators who wished to see the station open at the same time as St Pancras International, the Government failed to provide additional funding to allow the fit out works to be completed immediately following the line blockade.
Eventually, on 8 February 2006, Alistair Darling, the Secretary of State for Transport, announced £50 million funding for the fit-out of the station, plus another £10–15 million for the installation of associated signalling and other lineside works.

The fit-out works were designed by Chapman Taylor and Arup (Eurostar) and completed by ISG Interior Plc Contractors collaborating with Bechtel as Project Managers.
The client was London and Continental Railways who were advised by Hitachi Consulting.

In 2005, planning consent was granted for a refurbishment of the former Midland Grand Hotel building, with plans to refurbish and extend it as a hotel and apartment block.
The newly refurbished hotel opened to guests on 21 March 2011 with a grand opening ceremony on 5 May.
By the middle of 2006, the western side of the train shed extension was completed.
The rebuilding cost was in the region of £800 million, up from an initial estimate of £310 million.
By early 2004, the eastern side of the extended train shed was complete, and the Barlow train shed was closed to trains. From 12 April 2004, Midland Mainline trains terminated at an interim station occupying the eastern part of the extension immediately adjacent to the entrance.
As part of the construction of the western side of the new train shed that now began, an underground "box" was constructed to house new platforms for Thameslink, which at this point ran partially under the extended station. In order for this to happen, the existing Thameslink tunnels between Kentish Town and King's Cross Thameslink were closed between 11 September 2004 and 15 May 2005 while the works were carried out. Thameslink services from the north terminated in the same platforms as the Midland Main Line trains, while services from the south terminated at King's Cross Thameslink.
When the lines were re-opened, the new station box was still only a bare concrete shell and could not take passengers. Thameslink trains reverted to their previous route but ran through the station box without stopping. The budget for the Channel Tunnel Rail Link works did not include work on the fitting out of the station, as these works had originally been part of the separate Thameslink 2000 works programme.  Despite lobbying by rail operators who wished to see the station open at the same time as St Pancras International, the Government failed to provide additional funding to allow the fit out works to be completed immediately following the line blockade. Eventually, on 8 February 2006, Alistair Darling, the Secretary of State for Transport, announced £50 million funding for the fit-out of the station, plus another £10–15 million for the installation of associated signalling and other lineside works.
The fit-out works were designed by Chapman Taylor and Arup (Eurostar) and completed by ISG Interior Plc Contractors collaborating with Bechtel as Project Managers. The client was London and Continental Railways who were advised by Hitachi Consulting.
In 2005, planning consent was granted for a refurbishment of the former Midland Grand Hotel building, with plans to refurbish and extend it as a hotel and apartment block. The newly refurbished hotel opened to guests on 21 March 2011 with a grand opening ceremony on 5 May.
By the middle of 2006, the western side of the train shed extension was completed. The rebuilding cost was in the region of £800 million, up from an initial estimate of £310 million.
St Pancras railway station