A delivery device for deploying a self-expanding implant within a body cavity, the device comprising: at least one retention formation for holding the implant against axial or circumferential movement; an elongate longitudinally-extending outer element , radially outboard of the or each retention formation ; an imaging head disposed on a longitudinal axis that extends on a radially-inboard side of the or each retention formation ; and a handle connected to a proximal end of the outer element , the or each retention formation being fixed axially relative to the handle , and the outer element and the imaging head being movable axially relative to the handle ; wherein the outer element is movable bidirectionally in longitudinal directions relative to the handle between: a storage position in which the outer element surrounds the implant and holds the implant engaged with the or each retention formation ; and a partial-deployment position in which the outer element uncovers a distal portion of the implant while surrounding a proximal portion of the implant to continue holding the implant engaged with the or each retention formation ; and the imaging head is retractable in a proximal direction relative to the handle from: an advanced position when the outer element is in the storage position; to a retracted position when the outer element is in the partial-deployment position. at least one retention formation for holding the implant against axial or circumferential movement; an elongate longitudinally-extending outer element , radially outboard of the or each retention formation ; an imaging head disposed on a longitudinal axis that extends on a radially-inboard side of the or each retention formation ; and a handle connected to a proximal end of the outer element , the or each retention formation being fixed axially relative to the handle , and the outer element and the imaging head being movable axially relative to the handle ; wherein the outer element is movable bidirectionally in longitudinal directions relative to the handle between: a storage position in which the outer element surrounds the implant and holds the implant engaged with the or each retention formation ; and a partial-deployment position in which the outer element uncovers a distal portion of the implant while surrounding a proximal portion of the implant to continue holding the implant engaged with the or each retention formation ; a storage position in which the outer element surrounds the implant and holds the implant engaged with the or each retention formation ; and a partial-deployment position in which the outer element uncovers a distal portion of the implant while surrounding a proximal portion of the implant to continue holding the implant engaged with the or each retention formation ; and the imaging head is retractable in a proximal direction relative to the handle from: an advanced position when the outer element is in the storage position; to a retracted position when the outer element is in the partial-deployment position. an advanced position when the outer element is in the storage position; to a retracted position when the outer element is in the partial-deployment position. <EOS>