The HS2 revealed the final look of its tunnel portal in Buckinghamshire.

The high-speed railway revealed the final design for the North Portal of the Chiltern tunnel.

The portal design is the last of seven key structures along the HS2’s longest tunnel, which cuts across Buckinghamshire countryside.

Once the construction is complete, the seven ‘Key Design Elements’ will be the only visible part of the 10-mile tunnel.

Bucks Free Press: A CGI visual of the North Portal A CGI visual of the North Portal (Image: HS2 Ltd)

Other Key Design Elements alongside the North Portal between Great Missenden and South Heath include the South portal near the M25, headhouses used for ventilation and emergency access shafts designed to look like agricultural buildings.

HS2 Ltd’s design director Kay Hughes said: “The Chiltern Tunnel North Portal will be one of the least visible parts of the project, but today’s reveal of the final designs is a major symbolic milestone – and I’d like to congratulate Align on getting all their Key Design Elements to this final stage of development.”

What the North Portal will look like



The North Portal will be only partially visible from a footbridge over the railway to the north, HS2 said.

Two perforated concrete hoods will cover the track, extending the tunnel into the open air. These ‘porous portals’ will avoid sudden changes in air pressure – and resulting noise – caused by trains entering and exiting the tunnels.

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Alongside the portals, there will also be a simple single-storey ancillary building to house mechanical and electrical equipment which will be clad in earth-coloured pigmented zinc. After feedback from residents, the building was reduced in size and will now have a green roof to help further blend the infrastructure into the landscape.

The headhouses about the ventilation and emergency access shafts at Chalfont St Peter, Chalfont St Giles, Amersham, Little Missenden and Chesham Road are also designed to resemble agricultural buildings to better blend them with the landscape.