Bird & Bird has sealed a pre-let deal with Great Portland Estates (GPE) to move into new City premises at 12-14 New Fetter Lane from 2016.

The firm has agreed a deal to lease all of the 12-storey office development, which covers a total of 142,500 sq ft – an increase of around 17% on the firm's current City capacity.

Practical completion is scheduled for late 2015, with the firm retaining an option to hand back up to 25,900 sq ft six months before this point.

Bird & Bird currently takes up total of 122,000 sq ft across three buildings at 15 Fetter Lane, 90 Fetter Lane and 20 Furnival Street, housing a combined headcount of around 500. The current leases expire in 2016.

Rent for the new building will be charged at £8.7m per annum with the deal including an initial seven-month rent-free period. The agreement comprises four 20.25-year leases with no break clause, while GPE will provide £20.6m in cash spread over four quarterly instalments to cover fitting out and other costs.

Nabarro advised GPE on the deal – one of the developer's largest-ever pre-lets – with a team led by real estate partner Barry Morris and construction partner Alistair McGrigor. Real estate partner Deborah Parry is the firm's GPE relationship partner.

Meanwhile, a team from Simmons advised Bird & Bird led by real estate partner John Kelsey.

Bird & Bird CEO David Kerr said: "The arrangements enable us to make the move with minimal double overheads. Most importantly, the building will also offer a significantly improved client reception, hospitality and meeting space and will give us the opportunity to offer a range of facilities to our visiting clients.

"We feel the move reflects the firm's position as one of London's fastest growing law firms and provides room for our continued growth, reflecting our confidence in the future."