Mr William Day
College Position
Fellow in Law
Other Positions

Director of Studies in Law, College Associate Professor 

Degrees and Honours

MA, BCL (Oxon)

Research Interests

My primary research interests are in commercial law generally and particularly in the fields of economic torts, contract law, the law of restitution and the conflict of laws (also known as private international law). These coincide with the papers I teach at Downing and at the Faculty of Law (contract, tort, commercial, advanced private law) and also the main areas of my practice as a barrister at 3 Verulam Buildings.

My current projects include writing a textbook on commercial law and editing a collection of essays on private international law. I am also researching papers on undisclosed agency, contractual interpretation, and frustration.

I have published a number of articles and notes in journals including the Cambridge Law Journal, Law Quarterly Review and the Lloyd’s Maritime and Commercial Law Quarterly on a range of commercial law subjects, which have been cited by and to the Commercial Court, Court of Appeal and Supreme Court.

Select Publications



  • Key Ideas in Commercial Law (Hart, forthcoming, 2023)

Edited collections

  • Landmark Cases in Private International Law (Hart, forthcoming, 2023) (with Louise Merrett)
  • Challenging Private Law: Lord Sumption on the Supreme Court (Hart, 2020) (with Sarah Worthington)

Chapters in edited collections

  • ‘The Eleftheria’ in Landmark Cases in Private International Law (Hart, forthcoming, 2023)
  • ‘Justifications for and Limitations on Interventions by Undisclosed Principals’ in PS Davies and Tan CH, Intermediaries in Commercial Law (Hart, forthcoming, 2022)
  • ‘Variation and Waiver’ in Challenging Private Law: Lord Sumption on the Supreme Court (Hart, 2020)
  • ‘Proprietary Restitution’ in Challenging Private Law: Lord Sumption on the Supreme Court (Hart, 2020) (with Sarah Worthington)
  • ‘Disproportionate Penalties in Commercial Contracts’ in PS Davies and M Raczynska (eds), The Contents of Commercial Contracts: Terms Affecting Freedoms (Hart, 2020)


  • ‘In restraint of restraint of trade’ [2022] LMCLQ 134
  • ‘Recent travails of fraudulent misrepresentation’ [2021] LMCLQ 636
  • ‘Reliance: a comparison between the common law and s90A FSMA’ (2021) 36 JIBFL 389
  • ‘Contracts, illegality and comity: Ralli Bros revisited’ (2020) 79 CLJ 64
  • ‘A mistaken turn in the law of contractual misrepresentation’ [2019] LMCLQ 390 (with Paul S Davies)
  • ‘Reputation in the conflict of laws’ [2019] LMCLQ 1
  • ‘‘At the expense of’ in unjust enrichment: causal, direct or intentional transfers of value?” [2017] LMCLQ 588
  • ‘Against necessity as a ground for restitution’ [2016] RLR 26
  • ‘Skirting around the issue: the corporate veil after Prest v Petrodel’ [2014] LMCLQ 269

Case notes

  • ‘Pleading and proving foreign law’ (2022) 81 CLJ forthcoming
  • ‘Duress and uncertainty’ (2022) 138 LQR forthcoming
  • ‘Applicable law and arbitration agreements’ (2021) 80 CLJ 238 
  • ‘Remoteness in contract damages’ (2021) 80 CLJ 29
  • ‘Risks on the contract/unjust enrichment borderline’ (2020) 136 LQR 349 (with Graham Virgo)
  • ‘Freedom of contract and restraint of trade’ (2020) 79 CLJ 11
  • ‘Lawful act duress (again)’ (2020) 136 LQR 7 (with Paul S Davies)
  • ‘Piggyback jurisdiction and the corporate veil’ (2019) 135 LQR 551
  • ‘Isn’t Brexit frustrating?’ (2019) 78 CLJ 270
  • ‘Further narrowing the scope of unjust enrichment’ (2019) 78 CLJ 24
  • ‘Non-assignment clauses – the statutory solution’ (2019) 135 LQR 205 
  • ‘Restitution for wrongs: one step forward, two steps back?’ [2018] RLR 60
  • ‘Jurisdictional gateways in the CPR’ (2018) 77 CLJ  36
  • ‘Lawful act duress’ (2018) 134 LQR 5 (with Paul S Davies)
  • ‘Restitution for wrongs: one step in the right direction?’ (2017) 133 LQR 384
  • ‘A pyrrhic victory for the doctrine against penalties’ [2016] JBL 115 and 251
  • ‘Attributing illegalities’ (2015) 74 CLJ 409
  • ‘An application of Wrotham Park damages’ (2015) 131 LQR 218
  • ‘Negligence and the corporate veil: parent companies’ duty of care to their subsidiaries employees’ [2014] LMCLQ 454
  • ‘Penalty clauses revisited’ [2014] JBL 512
  • ‘Taking balance-sheet insolvency beyond the point of no return’ (2013) 72 CLJ 515

Book reviews

  • E Bant, K Barker and S Degeling (eds), Research Handbook on Unjust Enrichment (Edward Elgar, 2020): (2021) 80 CLJ (forthcoming)
  • C Mitchell and S Watterson (eds), The World of Maritime and Commercial Law: Essays in Honour of Francis Rose (Hart, 2020): (2020) 136 LQR 690
  • A Arzandeh, Forum (Non) Conveniens in England: Past, Present and Future (Hart, 2019): (2020) 79 CLJ 189
  • A Burrows, Thinking About Statutes: Interpretation, Interaction, Improvement (CUP, 2018): (2019) 78 CLJ 222
  • C Mitchell, P Mitchell and S Watterson (eds), Goff & Jones: The Law of Unjust Enrichment 9th edn (Sweet & Maxwell, 2016) and J Edelman and E Bant, Unjust Enrichment 2nd edn (Hart, 2016): [2018] RLR 280
  • C Witting, Liability of Corporate Groups and Networks (CUP, 2018): (2018) 34 JPN 163
  • G Virgo and S Worthington (eds), Commercial Remedies (CUP, 2017): (2018) 81 MLR 378
  • S Degeling and J Varuhas (eds), Equitable Compensation and Disgorgement of Profit (Hart, 2017): [2017] LMCLQ 606
  • PS Davies, Accessory Liability (Hart, 2015): (2015) 36 LS 382