Allen & Overy (A&O) arbitration partner Anthony Sinclair has joined Quinn Emmanuel Urquhart & Sullivan's London office following lengthy exit negotiations with his former firm.

Sinclair, who made partner at A&O last year, handed in his notice at the firm in May along with fellow arbitration partner Stephen Jagusch.

The move was followed by a statement from A&O that the pair had given notice of their intention to resign from the firm at the end of the 2013 financial year, suggesting the firm would be holding the partners to their contractual 12-month notice period.

At the time, Quinn Emmanuel managing partner John Quinn described the move as "unhelpful to clients", adding that it reflected badly on A&O; however, it is understood that Jagusch – a top-rated arbitrator who has been a partner at the magic circle firm since 2002 – will now start at Quinn at the beginning of 2013.

The appointments mark Quinn's first steps to set up a dedicated arbitration practice in London. Sinclair will work alongside of counsel Nontas Triantafilou, who joined the US firm from the Permanent Court of Arbitration at the Hague, where he was a legal counsel.

Sinclair commented that the team had started with a large workload, including taking an advisory role on a £250m investment treaty case for a former CIS state. "Watch this space; this practice is going to be a big deal in the City," he said.

Richard East (pictured), the co-managing partner of Quinn's London office, said: "Adding a first rate international arbitration group to our existing litigation team was a natural extension of our dispute focused practice. It will not only benefit London but all the firm's practices."

Sinclair described the move as "an offer I could not refuse", with Quinn adding: "We are not going to stop here. We plan to add leading practitioners in all the world's major arbitration centres."

The fast-growing firm has earmarked Germany, Switzerland and Singapore for office launches within the next two years as part of ambitious expansion plans across Asia and Europe.

For more, see Quinn to strengthen City arbitration with double partner hire from A&O.