A centraliser (112;212;312) for centralising tubing in a bore , comprising: end collars (120;220;320) connected by members (118;218;318;418), wherein the members (118;218;318;418) comprise an intermediate portion (119;219) and end portions (121;221) for connecting the intermediate portion (119;219) to the end collars (120;220;320), wherein the centraliser (112;212;312) is configurable between a larger diameter configuration in which the intermediate portion (119:219) assumes a radially outer position with respect to the centraliser (112;212;312) and a smaller diameter configuration in which the intermediate portion (119;219) assumes a radially inner position, wherein the end portions (121;221) are configured to permit movement of the intermediate portion (119;219) between the radially outer and inner positions, and the intermediate portion (119;219) is relatively less flexible than the end portions (121;221), wherein the members (118;218;318;418) are integral with the end collars (120;220;320), wherein the intermediate portion (119;219) comprises a curved section, defined in a direction along members (118;218;318;418), defining a first radius of curvature for providing the intermediate portion (119;219) with relatively less flexibility than the end portions (121;221), wherein the end portions (121;221) comprise a curved section , defined in the direction along the members (118;218;318;418), defining a second radius of curvature, the second radius of curvature being greater than the first radius of curvature, for permitting movement of the intermediate portion (119;219) between the radially outer and inner positions, and wherein the intermediate portion (119;219) defines a convex outer surface defined in a direction along the members (118;218;318;418) and the end portions (121;221) define a concave outer surface defined in the direction along the members. end collars (120;220;320) connected by members (118;218;318;418), wherein the members (118;218;318;418) comprise an intermediate portion (119;219) and end portions (121;221) for connecting the intermediate portion (119;219) to the end collars (120;220;320), wherein the centraliser (112;212;312) is configurable between a larger diameter configuration in which the intermediate portion (119:219) assumes a radially outer position with respect to the centraliser (112;212;312) and a smaller diameter configuration in which the intermediate portion (119;219) assumes a radially inner position, wherein the end portions (121;221) are configured to permit movement of the intermediate portion (119;219) between the radially outer and inner positions, and the intermediate portion (119;219) is relatively less flexible than the end portions (121;221), wherein the members (118;218;318;418) are integral with the end collars (120;220;320), wherein the intermediate portion (119;219) comprises a curved section, defined in a direction along members (118;218;318;418), defining a first radius of curvature for providing the intermediate portion (119;219) with relatively less flexibility than the end portions (121;221), wherein the end portions (121;221) comprise a curved section , defined in the direction along the members (118;218;318;418), defining a second radius of curvature, the second radius of curvature being greater than the first radius of curvature, for permitting movement of the intermediate portion (119;219) between the radially outer and inner positions, and wherein the intermediate portion (119;219) defines a convex outer surface defined in a direction along the members (118;218;318;418) and the end portions (121;221) define a concave outer surface defined in the direction along the members. <EOS>