In addition to regeneration of the existing station, a new section will be built to the west of the current 1960s Euston building. The HS2 expansion will have its own entrance, which will be covered by a petal-shaped yellow roof and include space for shops, restaurants and cafes.
Eleven new platforms are now proposed to be constructed at the station in two phases – the first, in 2026, will see six high-speed platforms added, and the second will take place seven years later to deliver five additional platforms by 2033.
Underground facilities will also be improved, with a new ticket hall and a subway to Euston Square station.
According to a statement from HS2, the plans include the possibility for redeveloping the platforms and concourses in the original Euston Station, although this is subject to funding and approval.
Opened in 1837, Euston station was demolished and rebuilt in 1968. Originally designed for 20 million passengers a year, the station now seres more than 42 million annually, making it the sixth busiest terminal in London.
"It's time for Euston to change," HS2 Chief Executive Simon Kirby said in a statement. "Not just to fulfil its historic role as the gateway between London and much of the rest of the country, but also if it's to become a much bigger and fully accessible part of its own community."
"Just a stone's throw away, we have seen how the stations at King's Cross and St Pancras have transformed the surrounding areas into vibrant and thriving locations. We must replicate and build on that commercial and architectural success," he added.
London's transport network is undergoing major development, with the construction of the Crossrail line – which will feature trains designed by Barber and Osgerby. The roof garden of Foster + Partners' Canary Wharf Crossrail station has already opened to the public, while work has started on a public square underneath Richard Seifert's iconic Centre Point tower as part of the project.
Meanwhile architecture firm NBBJ has suggested a more whimsical alternative solution to London's commuter chaos, proposing to transform the Circle Line into a giant travelator.