Abstract: An electrical heater for clamping round a body to be heated comprises a sheet-like elongate heating element, a housing member against which the element is located, and a continuous band of flexible metal strip formed into two closely-spaced elongate sections joined at their ends by rounded sections. The element is sandwiched between the housing member and one of the elongate sections and that section is slidably attached to the housing member. In use, the heater is located round the body with the housing member in contact with the body, and the rounded end sections of the strip are urged together, for example by a screw cooperating with rollers within the rounded sections.