Giving the ruling, Lord Justice Holgate said the tunnel extension and portal were authorised by the 2017 act, but that the planning permission under the act did not apply.
When the tunnel’s construction was authorised, the western portal was to be in Washwood Heath and the eastern portal in Castle Bromwich.
Both of these were located in the area of Birmingham City Council.
During 2020, HS2 decided the tunnel should be extended to the east by a further 2.9km (1.8 miles), so the tunnel would have an overall length of 5.8km, double the length of the original tunnel.
The tunnel’s eastern portal would be constructed further to the east so as to emerge in Water Orton, which is not under the city council.
A spokesperson for the North Warwickshire council said this change brought “[considerably] more construction and destruction to Water Orton”.
“Despite initially agreeing that the extension needed a separate planning application and environmental assessment HS2 Limited changed their minds and appealed to a Planning Inspector,” the spokesperson added.