Simon originally qualified as a solicitor before transferring to the Bar. He was one of the few solicitor-advocates qualified in both civil and criminal proceedings. He has exercised higher rights, including before the Supreme Court in a key secret justice case, since 2003.

His experience as a solicitor means he understands the pressures on those who instruct him and can often assist with an early and informal view on the merits of a case, advice and assistance on case management and, where necessary, preparation.

Simon has been involved in some of the country’s most high profile and sensitive cases.

Photo: Simon lecturing on investigatory powers for the American Bar Association

He has advised the government on national security-related matters, domestic and international counter-terrorism operations and the whole range of surveillance law issues (from interception, equipment interference and other covert surveillance to informers and witness protection matters). He was one of the Attorney General’s Special Advocates (Terrorism) for ten years and retains his expertise in the handling of sensitive intelligence, disclosure, terrorism and other national security-related law generally (such as, for example, Official Secrets Act offences).

Simon is the author of the leading textbook on the interception of communications, informers, encryption and covert surveillance law: Covert Policing Law & Practice published by Oxford University Press.


Crimeline described it as “certainly not the only book available that discusses the wider implications of RIPA, but it is the most up to date and the best”.

“If you are a practitioner embroiled in a case (or cases) in which covert policing is a key issue (or even a peripheral one) this is an important work of reference you really do need to acquire” Phillip Taylor MBE and Elizabeth Taylor of Richmond Green Chambers


An entirely new text, Covert Investigatory Powers Law & Practice is due to be published by Elgar in 2024.

Simon also wrote Blackstones’ Guide to the Investigatory Powers Act 2016 (published November 2017) and jointly written chapters for other books.

He frequently writes papers and articles for peer-reviewed publications and the news media and for the legal press.

Simon’s practise encompasses acting in and advising on serious criminal matters (he is often brought into ongoing cases to advise on surveillance law issues involving intercept, electronic surveillance, informers and undercover policing), judicial reviews, media law, advisory work on the Investigatory Powers Act 2016 and civil claims (actions for/against the state, misuse of private information, civil claims for unlawful interception).

His advocacy has been the subject of positive judicial comment, the former Lord Chief Justice, Lord Thomas referred to his “realism and strength of advocacy” and that he had argued his case “responsibly, attractively and with vigour” and Wyn Williams J said he “argued [his client’s] case with conspicuous skill and moderation”.

Simon McKay remains committed to practising in both the civil and criminal jurisdictions in England, Wales and Northern Ireland.