A robot comprising: a base； a flexible arm extending from the base and having: a plurality of joints whereby the configuration of the arm can be altered, a plurality of drivers arranged to drive the joints to move, and an attachment structure for attaching a tool to the arm； and a control unit configured to control the drivers and to receive inputs from sensors, and operable in a mode in which, whilst a tool is attached to the attachment structure and captive in a port, it: (i) controls the drivers to permit the arm to be reconfigured by the action of an external force applied to the arm so as to cause the tool to be retracted from the port along a longitudinal axis of the tool； and (ii) on receiving sensor input indicating that the arm has been reconfigured so as to cause the tool to be retracted from the port along a longitudinal axis of the tool, controls the drivers to reconfigure the arm so as to agitate the tool transverse to the longitudinal axis of the tool.
