Ms Long, who previously spent a number of years working with Matheson, rejoins the firm from the OECD in Paris, where she spent a number of years working with its tax treaty unit.

As well as her work on tax treaties, she was heavily involved during her time at the OECD in the development of the Two-Pillar Solution, the OECD’s flagship project.

Shane Hogan, head of tax at Matheson, said: “We are delighted to welcome Olivia back to Matheson’s tax practice to lead our tax policy function.

“Her experience, which included negotiating with government officials from around the world to agree the new international tax framework, is unique in the Irish market and will further enhance the ability of Matheson’s tax team to advise clients on the impact of the rapidly changing tax landscape on strategic business decisions.

“This senior appointment further distinguishes our tax practice in the Irish market and underlines our position as tax law firm of choice for internationally focused companies doing business in and from Ireland, and I am looking forward to working closely with her over the coming years.”

Matheson’s tax practice includes over 50 lawyers and around 20 partners.