The major new building complex is being brought forward by joint venture development between Stanhope and Mitsui Fudosan UK.

A significant part of the building will be developed as commercial office space allowing the British Library to develop the site and take over 100,000 sq ft at no extra cost to the taxpayer.

Architect Rogers Stirk Harbour + Partners has drawn up plans with support from engineer Arup to build out the largely undeveloped 2.8 acres at the rear of the existing building, creating a new Knowledge Quarter and home for the Alan Turing Institute.

The project involves the demolition of buildings on the site north of the library, including the Long and Kentish-designed British Library Centre for Conservation

It will also include extensive underground enabling works at part of the site for the proposed Crossrail 2 station which would link the Euston and St Pancras stations to create a major transport interchange.

The new library building includes three basement levels which will connect into the existing building, a large foyer and offices above.

Both the early underground station works and library space will be funded by 770,000 sq ft of commercial space in the building complex.

The British Library expects to submit for planning in late Spring with construction due to start in late 2023.