A control instrument 100 for a guidewire comprising a first component moveable from a first position, in which the guidewire can move axially relative to the first component, to a second position in which the guidewire is fixed relative to the first component and a second, rotatable, component, wherein rotation of the second component causes the first component to move axially, only when the first component is in its second position, thereby moving the guidewire move axially.
