John Hayes

About the LawyerJohn Hayes is a leading employment lawyer in London and the founder of Constantine Law. He specializes in advising UK corporates across various sectors, including financial services, employment agencies, retail, and construction. His approach is solutions-oriented and commercially focused, making him a trusted advisor for businesses seeking employment and labour law guidance.In addition to his role at Constantine Law, John’s entrepreneurial client base and experience in the employment sector motivated him to establish the firm in 2015. Prior to founding Constantine Law, he headed the London employment team of a large national law firm. John is a member of the Employment Lawyers Association, the Irish International Business Network (IIBN), the Institute of Directors (IOD), and the American Bar Association. He is also active in media and trade publications on employment and labour law topics and hosts an employment law podcast, where he discusses current developments and practical issues affecting employers and workers.As the founder and Managing Partner of Constantine Law, John has played a central role in shaping a modern, entrepreneurial employment and labour practice focused on agile, commercially driven solutions for UK employers and senior executives.ExperienceJohn has a distinguished career in labour and employment law, having qualified as a barrister in 1993 and as a solicitor in 2001. He is a skilled advocate with extensive experience litigating in employment tribunals and the Employment Appeal Tribunal, handling cases related to unfair dismissal, whistleblowing, and equal opportunities. John is also highly experienced in High Court practice, particularly in restrictive covenant disputes, where he has successfully obtained numerous injunctions for leading corporate clients.Over more than three decades in practice, John has focused on advising UK corporates on labour and employment issues across financial services, employment agencies, retail, and construction. His client base is predominantly entrepreneurial, and he regularly advises senior executives and owner-managed businesses on contentious and non-contentious labour matters, including exits, disputes, and negotiations involving employment status and contractual protections.Before establishing Constantine Law in 2015, John headed the London employment team of a large national law firm, leading on complex labour and employment mandates and High Court litigation. Since founding Constantine Law, he has been instrumental in building it into a leading employment and labour law firm in London, with a particular emphasis on providing commercial, solutions-oriented advice to middle-market employers and high-profile corporate clients.SpecialtyJohn’s legal expertise is primarily in labour and employment law with an emphasis on business protection. He works closely with leading barristers to safeguard his clients’ commercial interests in the context of workplace relations, workforce structuring, and the protection of confidential information and key personnel.His specializations include consultancy agreements, IR35, the Construction Industry Scheme (CIS), and the associated tax implications as they affect employment status and labour supply chains. He collaborates with accountants to deliver integrated legal and financial solutions in these areas, particularly for employers and agencies managing complex workforces and atypical working arrangements.John is recognized for his work in restrictive covenant disputes and large-scale employment status matters, often representing major employment agencies and other significant employers. His practice covers defending whistleblowing claims, advising on equal opportunities and discrimination issues, and addressing the labour law dimensions of flexible, contingent, and atypical working models. He also advises on strategic workforce issues arising from regulatory change and evolving case law in UK labour and employment law.EducationJohn qualified as a barrister in 1993 and later as a solicitor in 2001, reflecting a dual background that underpins his strengths in advocacy and litigation within labour and employment law. Specific details regarding his academic degrees or the universities he attended are not publicly available.

• Awards / Recognition: John Hayes is identified by Legal 500 as an experienced advocate in employment law, and the profile states that Constantine Law was founded by John Hayes, described there as “one of London’s leading employment lawyers.”
• Industry rankings: Chambers profiles John Hayes as the founder and partner at Constantine Law with experience handling employment matters, including for senior executives.
• Leadership roles: John Hayes is recognized as the founder and Managing Partner of Constantine Law.
• Major case successes: Constantine Law’s site states that John Hayes has obtained numerous injunctions for corporate clients in the High Court in recent years.