The deal to take 610,000 sq ft paves the way for work to start on 11 and 21 Canal Reach and P2, the last major sites on the long-running regeneration scheme.

While not quite the same scale as the Google HQ at 1m sq ft on the site, it ranks as one of the most significant commercial deals in London this decade – booking 15% of the total 4m sq ft commercial space at King’s Cross at a stroke.

Curving facade of the Canal Reach buildings seen from HS1 railtracks

Buildings 11 and 21 Canal Reach have been designed by architect Bennetts Associates and have detailed planning permission, featuring 10 and 12 floors of modern Grade A office space respectively (415,000 sq ft in total).

With expansive double-height receptions and 42,000 sq ft of landscaped roof gardens and terraces, the buildings located in the ‘Western Yards’ of King’s Cross offer their users uninterrupted views over Central London.

Contractor BAM had previously been mooted as the likely builder for the two curving office blocks on the northern part of the site. But it is not known yet whether Facebook will want to appoint its own builder through a fresh tendering process.

P2 on Lewis Cubitt Square, for which a reserved matters planning application was submitted in June, is designed by Allford Hall Monaghan Morris.  It will provide nine floors of office space (196,000 sq ft), alongside a new theatre for London, a fifth-floor wraparound terrace and retail space at ground level.

Facebook plans to open its new offices in King’s Cross in 2021.