Wills Act 1837 -UK

the word “will” shall extend to a testament, and to a codicil, and to an appointment by will or by writing in the nature of a will in exercise of a power, and also to an appointment by will of a guardian of a child,and also to an appointment by will of a representative under section 4 of the Human Tissue Act 2004 or section 8 of the Human Transplantation (Wales) Act 2013,  and to any other testamentary disposition;