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Two new Associate Members

New Chambers welcomes two new Associate Members, Mark Costello KC and Joshua Thomson SC.

Mark practises in all areas of commercial litigation as well as constitutional and administrative law. He has appeared in courts in all states and has also appeared before various arbitral tribunals.

His commercial law experience spans class actions, contract disputes, competition law, corporate insolvency, engineering disputes, professional indemnity claims and regulatory litigation.

His public law experience includes a broad range of constitutional and administrative law litigation and advice, from the Administrative Appeals Tribunal through to the High Court of Australia.

He has appeared in various Royal Commissions, including as Counsel Assisting the Financial Services Royal Commission.

He was previously a Senior Fellow of the Monash University Faulty of Law.

Before coming to the Bar, Mark was a commercial litigation solicitor with Minter Ellison and Arnold Bloch Leibler and an Associate to a Justice of the High Court of Australia.


As the former Solicitor-General of WA, Joshua has acted for the State of WA in the High Court of Australia on all cases of major importance for the State, including significant cases about s 92 and Ch III of the Constitution. He has personally advised the Premier and the Attorney General of Western Australia, been involved in reviewing draft legislation, and provided constitutional and other advice to Ministers and other State entities.

Prior to his appointment as the Solicitor-General, his practice covered a wide range of areas, including contractual and insolvency disputes, building and construction matters, maritime law, regulatory competition law for pipelines, professional negligence and insurance law, administrative and constitutional law and native title claims. He has conducted lengthy trials and complex appeals, and provided strategic advice to major clients, such as international and national banks in a complicated construction and insolvency dispute (4-5 month trial and lengthy appeal); insured directors and officers in a major mining matter; and receivers and managers in several complicated receiverships.


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