It is almost inconceivable to direct or manage a business portfolio or a programme without having to deal with contracts. For some organizations, the bulk of their work is undertaken by third parties, whether for building infrastructure or for outsourcing. A customer and a supplier are parties to the contract. Parties are those with a legal, contractual relationship. A party can be any legal entity such as a person, or in the context of this book, most likely a formally constituted company, partnership or public sector or charitable body. English contract law evolves continuously as it builds on case law, resulting from judgements made over 150 years of disputes. The fact that contract law is based on case law has practical implications; in the case of a dispute, there is no easy way for the layman to find out what their legal position is.