A downhole isolation valve for testing the integrity of a tubular within a wellbore includes a tubular body with an axial through bore having a reduced diameter portion defining a valve seat and a ledge; an inner sleeve, with a closed end configured to seal within the valve seat, a shoulder spaced from that closed end, and a radial outlet positioned between the shoulder and the closed end; wherein in use the inner sleeve is selectively moveable within the bore at a predetermined pressure between a closed position, in which there is no flowpath through the bore, and an open position, in which the closed end is positioned beyond the valve seat to expose the radial outlet to the through bore beyond the valve seat and provide a flowpath through the bore of the outer tubular body.