A head-mounted display image delivery system in combination with a head-mounted display, HMD, device, the image delivery system and the HMD device being local to one another: • the HMD device comprising: one or more displays; one or more sensors (4,5,6) to determine movement, position and attitude of the display; and one or more image inputs configured to receive image data for direct display on the one or more displays without image processing by the HMD from the image delivery system, • the image delivery system being configured to communicate a stereoscopic image to the HMD device to convey image information to a wearer, wherein the image delivery system comprises: one or more inputs to receive sensor data from the sensors; one or more image inputs configured to receive pre-processed image data for direct display of the field of view on the one or more displays without image processing by the image delivery system and wherein the delivery system receives, in use, the pre-processed image data of the field of view; and one or more image outputs to deliver image data for direct display on the one or more displays of the field of view without image processing by the HMD system characterized in that said image delivery system is configured to receive additional pre-processed image data of images outside the field of view and not yet displayed on the display. • the HMD device comprising: one or more displays; one or more sensors (4,5,6) to determine movement, position and attitude of the display; and one or more image inputs configured to receive image data for direct display on the one or more displays without image processing by the HMD from the image delivery system, one or more displays; one or more sensors (4,5,6) to determine movement, position and attitude of the display; and one or more image inputs configured to receive image data for direct display on the one or more displays without image processing by the HMD from the image delivery system, • the image delivery system being configured to communicate a stereoscopic image to the HMD device to convey image information to a wearer, wherein the image delivery system comprises: one or more inputs to receive sensor data from the sensors; one or more image inputs configured to receive pre-processed image data for direct display of the field of view on the one or more displays without image processing by the image delivery system and wherein the delivery system receives, in use, the pre-processed image data of the field of view; and one or more image outputs to deliver image data for direct display on the one or more displays of the field of view without image processing by the HMD system characterized in that said image delivery system is configured to receive additional pre-processed image data of images outside the field of view and not yet displayed on the display. one or more inputs to receive sensor data from the sensors; one or more image inputs configured to receive pre-processed image data for direct display of the field of view on the one or more displays without image processing by the image delivery system and wherein the delivery system receives, in use, the pre-processed image data of the field of view; and one or more image outputs to deliver image data for direct display on the one or more displays of the field of view without image processing by the HMD system characterized in that said image delivery system is configured to receive additional pre-processed image data of images outside the field of view and not yet displayed on the display.