Following a recent high-profile case in which a regulatory, strict liability offence was utilised to provide the "unlawful act" in unlawful act manslaughter, this article examines what is a sufficiently "unlawful" act to underpin that offence. It argues that the breadth of offences that can now be used to found an unlawful act manslaughter charge has led to a departure from the fair-labelling principle and traditional notions of culpability. Even the traditional argument, that the requirement of dangerousness sufficiently circumscribes those offences that qualify, has been weakened as that requirement has been diluted, and no longer provides adequate protection. Considering the legal position when a death resulted from a collision with a bike which did not comply with a Regulation, this article argues that trying to use unlawful act manslaughter to fill a lacuna in the law relating to fatal collisions involving cyclists risks unfairness to defendants through the unwarranted expansion of liability. New legislation is likely to be the most appropriate way properly to criminalise riding falling below the standard of a reasonable cyclist, but not amounting to gross negligence, that causes death.