A safety valve (4) incorporated in a tubing string (2) has a diameter considerably larger than that of the rest of the tubing string (2). A cable protector (10) is fastened onto the tubing string (2) at the lead in to the safety valve (4) to ensure that cables (8) extending along the outside of the tubing string are able to cope with the changes in diameter without strain or damage. The cable protector (10) is formed from two cast bodies (12) and (14) hingedly connected together to define a substantially circular inner cross-section. The upper body member (12) is provided with an elongate cable slot (26) in which the cable (8) is received. In addition, the upper body member (12) is shaped to give the cable protector an increasing internal cross-sectional size, or transverse dimension, along its length from one end (B) to the other end (B'), whereby the distance of the cable (8) from the longitudinal axis (X-X) of the tubing string (2) increases as it extends therealong. Thus the cable (8), received within the cable slot (26), is guided along a path which has a varying spacing from the longitudinal axis (X-X).