Freshfields Bruckhaus Deringer and Allen & Overy (A&O) have taken lead roles on the merger of the London Stock Exchange (LSE) with TMX Group, which owns and operates the Toronto Stock Exchange.

Freshfields is fielding a team led by corporate partners Philip Richards and Andrew Hutchings on the deal, which will combine Europe's and Canada's leading diversified exchange groups.

Other partners on the Freshfields team include Jonathan Cooklin (tax), Jocelyn Mitchell (employment and share schemes) and Simon Priddis and Tom Ensign (competition).

Hutchings also advised the LSE on contested bids from Australian bank Macquarie and US exchange Nasdaq in 2005 and 2006, as well as the exchange's 2009 acquisitions of Sri Lanka capital markets technology company Millennium IT and rival trading platform Turquoise.

Meanwhile, A&O is acting for TMX, with London corporate partner Richard Evans heading up the firm's team. Canada's Osler Hoskin & Harcourt is advising the LSE on Canadian law, while Toronto-based firm Torys is acting for TMX.

Herbert Smith has also landed a role on the deal, advising banks Barcap and Morgan Stanley, which acted as sponsors. Corporate partner Greg Mulley is taking the key role for the firm.

The merger has been unanimously recommended by the boards of both the London Stock Exchange Group and TMX. If confirmed, it will create the world's fourth-largest trading centre as well as the biggest trading centre for mining and energy shares.

The combined transatlantic group will be jointly headquartered in London and Toronto, with more than 6,700 companies listed on the combined exchanges with a total market capitalisation of about £3.7trn.

LSE chief executive Xavier Rolet will head the new enlarged business, while TMX's chief executive Thomas Kloet will become president.