*William Tyzack

Year of call: 2007

*William *William

William joined Guildhall as a door tenant in 2019. He continues to practise from Queen Elizabeth Building in London.

A large part of William’s practice involves complex financial claims on divorce, frequently involving trusts, companies and conflicts of law issues. Cases involving private international law and the application of EU regulations form a major part of his practice. He is often instructed in child abduction cases under the 1980 Hague Convention and in applications for relocation. William has advised solicitors on English law across many EU & worldwide jurisdictions and has provided written and oral evidence on English law in foreign courts. He has lectured on international law issues both in the UK and abroad. William has acted on behalf of trustees, beneficiaries and companies, and has advised and represented clients in applications under the Inheritance (Provision for Family and Dependants) Act 1975.

Alongside this, William practises in the Court of Protection in cases relating to both health and welfare and property and financial affairs. He has been instructed in complex financial cases involving breaches by donees and deputies of their fiduciary duties, challenges to the validity of lasting powers of attorney and decisions in relation to the use of P’s assets. In respect of health and welfare, William has been instructed in cases involving care issues, serious medical treatment and the removal of P from the jurisdiction. He has acted in cases involving vulnerable adults under the inherent jurisdiction, and has experience of cases involving wider areas of public law.

Administrative & Public Law

William has been instructed in a number of recent cases in a public law context:

  • on behalf of the charity Rights of Women in respect of a challenge to the compliance of a statute with common law or Convention rights;
  • a claim under the Human Rights Act 1998 for damages against a local authority for breach of deprivation of liberty safeguards;
  • an application before the President (Re W [2017] All ER (D) 88) for disclosure of confidential documents from public law proceedings into a proposed civil action for misfeasance in public office.

William has experience of cases involving immigration and national security issues, and was appointed in 2018 to the Attorney General’s Panel of Special Advocates.

Court of Protection

William acts in Court of Protection cases involving all aspects of health and welfare and property and financial affairs.

He has provided training to solicitors on the law relating to mental capacity and is the correspondent of the Elder Law section of the Private Client Business journal.

International & Offshore

William is regularly instructed in cases involving complex jurisdiction, forum and international enforcement issues under domestic and EU law. He has represented private individuals and companies in cases in the English courts involving:

  • jurisdiction or forum conveniens issues;
  • worldwide freezing orders;
  • disclosure orders in support of foreign proceedings under the Civil Jurisdiction and Judgments Act 1982;
  • anti-suit injunctions;
  • applications for a stay of English proceedings due to the existence of related or connected foreign actions.

On a number of occasions William has been asked to provide expert evidence to foreign courts on English law or the English court’s approach to aspects of EU law.

Reported Cases

  • Uhd v McKay (Abduction: Publicity) [2019] 2 FLR 1159
  • Kelly v Pyres (Domicile) [2019] 1 FLR 62
  • J v U (Child Arrangements Order: Jurisdiction) [2017] 2 WLR 760
  • Hayatleh v Mofdy (Presumption of Marriage) [2017] EWCA Civ 70
  • Re W (Children) [2017] All ER (D) 88
  • Re R (Reunite International Child Abduction Centre and others) [2015] 2 WLR 1583
  • AB v JJB (EU Maintenance Regulation: modification procedure) [2015] 2 FLR 1143
  • C v B [2014] EWHC 2069
  • EY v RZ [2013] EWHC 4403 (Fam)
  • FL v Registrar General [2011] 2 FLR 630


For further information and enquiries please contact: Stephen Arnold or Olive Kavanagh


  • Attorney General’s Panel of Special Advocates
  • Member of the Legal Working Group of Reunite Child Abduction Centre


  • Court of Protection Practitioners’ Association
  • Family Law Bar Association
  • Administrative Law Bar Association
  • Western Circuit


  • Middle Temple Diplock scholar, Harmsworth exhibition and CPE scholarship
  • BA (Oxon) First Class
  • LLM (UCL) Distinction