Domesticated and kept animals have the status of property at common law.  While this persists, it is essential that they are protected by legislation.  The cornerstone of such animal protection legislation is a cruelty offence - an entirely legal concept - which is defined by reference to causing unnecessary suffering.   While the scope of the offence is significantly wider in the UK than many other jurisdictions, it is committed only once an animal has suffered.  However, during the past 50 years the notion of welfare - a scientific concept - has developed into a discrete area of research, leading to legislation concerned with an animal's quality of life.  More recently, sentience and greater regard to the implications of evolutionary biology are having an impact on public policy and raising important issues about the scope and nature of animal protection legislation.  So, too, is increased concern about the environment, including concern for the welfare of wildlife - which raises fundamental issues about what the term 'welfare' means in this context.