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John Hayes
Constantine Law was founded by John Hayes, one of the UK’s leading employment lawyers, recognised in the Legal 500 and Chambers. He is busy scaling the UK’s leading employment law boutique.
John completed six High Court injunctions during 2025 and is currently acting in London’s biggest whistleblowing case. He advises businesses, law firms, senior executives and lawyers on complex restrictive covenant, strategic advisory, discrimination and team move cases.
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'John Hayes is very commercial, handles clients very well and gives them confidence. He always goes out to bat for the client and is very good with them' Chambers 2026
Position
Managing Partner
Contact
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Tenacious and direct, John is also one of London's leading solicitors in restrictive covenant disputes and an experienced High Court practitioner. He has obtained numerous injunctions for a range of corporate clients, in the High Court, in recent years, including in employment agency, wealth management and retail sectors. During 2025 he represented a national employment agency business in the Court of Appeal on an employment status case.
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During the past year he has represented and won in the High Court for three high profile senior executives including in the Tom James -vs- Max Potter case, which was widely reported in the national and legal press.
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John and Constantine Law are active members of the Employment Lawyers Association and John is a mentor to younger lawyers through ELA. He has also appeared on various ELA working parties, including the current Government consultation on restrictive covenants. John qualified as a solicitor in 2001 and as a barrister in 1993.
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John counts as his client base some of London’s best established and owner-managed recruitment, construction, legal, wealth management and public affairs businesses. He is an entrepreneur and he networks with and supports the work of our entrepreneurial community. Constantine law is an integral part of that community.
He has great experience in the arena of employment status, including consultancy agreements, IR35, CIS and the tax implications of each. He works closely with leading accountants to provide joined-up solutions for his clients.
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John writes regularly in the national and trade press on employment law subjects and you can access some of these articles here. He contributes regularly on the TV and radio.
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John is married and lives in Hampstead, London. He is a member of the Hampstead Triathlon Club and raises money through Olympic distance triathlons. His other main passions are public affairs, his local (north London) football team and London's cultural scene.
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