A steerable catheter, comprising: a catheter having a proximal first end portion, an elongate intermediate portion, a flexible distal second end portion (18, 22) articulatable from a relaxed position to a bending position (80, 90), and a substantially central longitudinal axis extending from the first end portion to the flexible distal second end portion, the flexible distal second end portion further comprising an outer circumference relative to the central longitudinal axis; an elongate chamber body (30, 34, 38, 42) having a proximal opening (31, 35, 39, 43) at or near the catheter proximal first end portion and terminating at an elastically fluid-distensible occluded distal end (32, 36, 40, 44) positioned within the catheter flexible distal second end portion and defining a longitudinal fluid channel (33, 37, 41, 45) that extends longitudinally between and in communication with the chamber body proximal opening and the chamber body occluded distal end, the chamber body occluded distal end being radially offset relative to the central longitudinal axis; and wherein the elongate chamber body occluded distal end is configured to elastically distend axially under a change in internal fluid pressure without substantially changing the catheter flexible distal end portion outer circumference and thereby articulate the catheter flexible second end portion from the relaxed position to the bending position; wherein the catheter flexible distal second end portion further comprises a flexible steerable distal tip portion containing said chamber body elastically fluid-distensible occluded distal end; wherein the flexible distal second end portion has a first outer diameter and the steerable distal tip portion has a second outer diameter that is smaller than the first outer diameter; characterised in that the flexible steerable distal tip portion has a core section in the form of a plug or filler for inhibiting radial inward expansion of said longitudinal fluid channel and said occluded end. a catheter having a proximal first end portion, an elongate intermediate portion, a flexible distal second end portion (18, 22) articulatable from a relaxed position to a bending position (80, 90), and a substantially central longitudinal axis extending from the first end portion to the flexible distal second end portion, the flexible distal second end portion further comprising an outer circumference relative to the central longitudinal axis; an elongate chamber body (30, 34, 38, 42) having a proximal opening (31, 35, 39, 43) at or near the catheter proximal first end portion and terminating at an elastically fluid-distensible occluded distal end (32, 36, 40, 44) positioned within the catheter flexible distal second end portion and defining a longitudinal fluid channel (33, 37, 41, 45) that extends longitudinally between and in communication with the chamber body proximal opening and the chamber body occluded distal end, the chamber body occluded distal end being radially offset relative to the central longitudinal axis; and wherein the elongate chamber body occluded distal end is configured to elastically distend axially under a change in internal fluid pressure without substantially changing the catheter flexible distal end portion outer circumference and thereby articulate the catheter flexible second end portion from the relaxed position to the bending position; wherein the catheter flexible distal second end portion further comprises a flexible steerable distal tip portion containing said chamber body elastically fluid-distensible occluded distal end; wherein the flexible distal second end portion has a first outer diameter and the steerable distal tip portion has a second outer diameter that is smaller than the first outer diameter; characterised in that the flexible steerable distal tip portion has a core section in the form of a plug or filler for inhibiting radial inward expansion of said longitudinal fluid channel and said occluded end.