Before the £500m development for the site at the rear of the existing building can proceed the London Mayor will have to give his final verdict on the plan.

Architect Rogers Stirk Harbour + Partners and engineer Arup have drawn up the plans. These include around 100,000 sq ft of new space for the British Library itself, and the station works infrastructure for Crossrail 2 beneath the site should it ever proceed.

The first three floors of the proposed extension will consist predominantly of the new British Library space, as well as retail and the entrances to the commercial space.

This public work would be funded by a further 600,000 sq ft of space available for commercial let targeting bioscience and knowledge quarter tenants.

Project timeline

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(l-r) Aerial of present site and the proposed extension located to the north of the existing Library building

• 2023–2025: We prepare the site for construction
• 2025–2029: Building begins and spaces are fitted out
• 2029: Our new spaces open to everyone

Cutaway of the proposed site showing the spaces dedicated to office and lab-enabled in relation to the existing British Library space

The proposed extension will open up public access to the library with new routes between Euston Road to the south and a new entrance beside Dangoor Walk to the north.

The foyer space will run through the middle of the two blocks and will be 8 storeys high, with bridges linking the two blocks together.