William is a Partner in Simpson Grierson's Litigation Department, advising on general commercial, civil, property and real estate litigation and licensing.  William is also one of New Zealand's foremost defamation and media lawyers.  He has appeared in numerous high profile High Court, Court of Appeal and Supreme Court media law cases, covering defamation, privacy, contempt, suppression orders, New Zealand Bill of Rights, Broadcasting Standards and censorship, and search of court records.

He has acted as general counsel to Television New Zealand for many years, and regularly provides pre-publication counselling.

He has also acted in many cases in the South Pacific - particularly in Samoa and the Cook Islands.  He has represented Governments and corporates in these jurisdictions in major constitutional, corporate, and international trust disputes.  He has a special interest in private international law.

• Re Goldcorp - High Court, Court of Appeal and Privy Council.  A leading authority on equitable remedies as relates to secured an unsecured creditors
• South Pacific Manufacturing Company v New Zealand Security Consultants - one of New Zealand's leading authorities in the law of negligence
• Hubble v Wrightsons Real Estate Ltd - a Court of Appeal decision involving the rights of real estate agents
• Stevens v Premium Real Estate - leading authority on the application of the Fair Trading Act as relates to real estate agents and breach of fiduciary duties
• Auckland Urban Council v Auckland City Council - judicial review proceedings under the Resource Management Act
• Hester v Commissioner of Inland Revenue - Court of Appeal decision on the application of the New Zealand Bill of Rights Act to taxation legislation
• Attorney General for the Cook Islands v Pitt - criminal libel in the Cook Islands
• Wignall v Matipo and the Henry Puna Electoral Challenge - constitutional cases in the Cook Islands Court of Appeal
• Acted for the Prime Minister, the Speaker of the House of Representatives, and the House of Representatives in major constitutional case in Samoa
• Acted for TVNZ in leading defamation cases - Quinn v TVNZ, currently acting for TVNZ in the largest defamation claim ever made in New Zealand courts
• Acted for TVNZ in leading cases on suppression orders and the open justice principle - TVNZ v R, Re Victim X, R v Liddell
• Acted for TVNZ in the leading authorities on search of court records - R v Mahanga, TVNZ v Mafart and Prieur
• Acted for TVNZ in major New Zealand case on confidentiality as relates to the media and disclosure of sources European Pacific v TVNZ
• Acted for TVNZ in contempt of court litigation Solicitor General v TV3 and TVNZ, Solicitor General v Berryman
• Acted for TVNZ in leading authority on editorial independence Meri Mungo v Television New Zealand Ltd
• Acted for TVNZ in leading authority on confidentiality as relates to Security Intelligence Services Her Majesty's Attorney General for England and Wales v Television New Zealand Ltd and X
• Acted for TVNZ in the Ahmed Zaoui case - freedom of expression as relates to those detained and held in custody as a security threat
• Acted for TVNZ in major cases on open justice and privacy -  Mafart and Prieur v TVNZ (Court of Appeal) and Rogers v TVNZ (Supreme Court)
• Acted as plaintiff's counsel in a number of major defamation proceedings (settled prior to trial)
• Acted for plaintiffs in leading real estate liability case Stevens v Premium Real Estate
• Acted in the leading privacy cases in New Zealand Hosking v Runting, Andrews v TVNZ, and Noel Rogers v TVNZ (Supreme Court)

• Regional Vice Chair (Asia Pacific) for the Lex Mundi Entertainment and Media Practice Group
• International Media Liability - Civil Liability in the Information Age - Co-author of New Zealand chapter
• PLC Which Lawyer? (2006) - Recommended Lawyer
• The Asia Pacific Legal 500 (2001-2006) - Leading Dispute Resolution Lawyer
• Chambers Global Guide to the World's Leading Lawyers 2004 - Leading Litigation Lawyer and Media Expert
• University of Auckland School of Law - Guest Lecturer
• New Zealand Media Law Association - Executive Committee