Morgan Stanley is set to name Mark Rawlinson, a long-time corporate partner at law firm Freshfields Bruckhaus Deringer, as its new chairman of UK investment banking in an unusual move to lure a star dealmaker from the legal industry.

The appointment will cast Mr Rawlinson, who has been one of London’s leading lawyers on mergers and acquisitions in recent years, in a banking role for the first time in his more than three-decade long career.

Unlike the US market, where several top bankers have had experience working at elite law firms, it is rare for an established UK lawyer to jump into investment banking.

The appointment is set to be announced on Monday, according to people briefed on the move, who added that Mr Rawlinson would begin at the bank in October and continue to be based in London. He will report to Franck Petitgas, Morgan Stanley’s global co-head of investment banking.

Morgan Stanley and Mr Rawlinson declined to comment.

Investment banks are finding it increasingly difficult to retain their most seasoned and best-known dealmakers at the pinnacle of their careers. Some, such as former Morgan Stanley bankers Simon Robey and Michael Zaoui, have quit to launch or join boutique advisory firms where they have more freedom to focus on clients and where they can earn bigger sums on individual deals because of low overheads.

Replacing senior bankers can be difficult, especially among a shrinking pool of candidates able to boast decades of experience. For instance, Deutsche Bank searched for months before eventually looking outside the banking industry to hire Thomas Piquemal, former finance director of French utility EDF, as its global head of M&A in May.

Mr Rawlinson joined Freshfields in 1982 and has held multiple roles, including the firm’s head of corporate and head of London, in his time at the firm. Over the past two years, Mr Rawlinson has worked on the largest deals in the UK market, including with BG Group, the oil and gas company, on its $52bn sale to Royal Dutch Shell, and AB InBev with its £71bn takeover of rival brewer SABMiller.

Thanks to those deals, Freshfields was the only non-US law firm to rank in the top 10 for global M&A market share last year, according to Dealogic data. He is also advising the London Stock Exchange Group on its pending £21bn merger with Germany’s Deutsche Börse.

Rob Kindler, Morgan Stanley’s global head of M&A, spent 20 years at US firm Cravath Swaine & Moore before joining the bank in 2000. The US bank sits in second place, behind Goldman Sachs, in league table rankings, having advised on $307bn of deals this year, according Thomson Reuters.