Linklaters and SJ Berwin have taken lead roles on the £340m development and pre-let of the new UBS headquarters on the Broadgate Estate in London.

Bluebutton Properties, a joint venture company owned by British Land and Blackstone, has secured a 700,000 sq ft pre-let with UBS at the estate.

The new building, when completed, will be the largest office block in the City.

Bluebutton was advised by SJ Berwin and Ashurst. SJ Berwin fielded a team led by real estate partners Rob Thompson and Lewis Myers, while partners Delphine Currie and Ian Borman advised on corporate and finance aspects of the deal respectively. Ashurst advised on construction, with partner Ann Minogue taking the key role.

UBS, which will pay an initial headline rent of £54.50 per square foot with a lease length of 18 years, instructed longstanding adviser Linklaters. The magic circle's real estate team was led by partner Anne Byrne, while construction partner Huw Baker, planning partner David Watkins and tax partner Gideon Sanitt also worked on the deal.

Lead partner Byrne commented: "We have a longstanding relationship with UBS – I have been working with them for over a decade now – and this was a particularly interesting deal to work on because it is the biggest office building in the City."

The completion of the building is expected in the second half of 2014, although this is subject to planning permission.

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