Section 230(3) of the Employment Rights Act 1996 defines a worker as an individual who has entered into or works under (a) a contract of employment or (b) any other contract, whether express or implied and (if it is express) whether oral or in writing, whereby the individual undertakes to do or perform personally any work or services for another party to the contract whose status is not by virtue of the contract that of a client or customer of any profession or business undertaking carried on by the individual.