A running tool for use in the insertion of an object such as a casing hanger into a subsea well includes a body and a hollow mandrel moveable within the body. Engagement dogs are supported within the body and are moveable to engage the object, the mandrel having a first part and a transition part, the transition part being shaped to cause out-ward movement of the dogs when the mandrel is in a given position within the body and to allow movement of the dogs for position of the mandrel spaced form the given position. The tool has an emergency release feature wherein the transition part is releasably attached to the first part by shear pins which shear in response to a sufficient increase in pressure within the mandrel to allow the transition part to separate from the first part.