Delivery devices

A device actuatable to deliver substance into a cavity, comprising:

• a delivery outlet from which substance is in use delivered;
• a gas chamber containing a gas and being of reducible volume, wherein a reduction in the volume of the gas chamber to a predetermined volume acts to pressurize the contained gas to a predetermined pressure;
• a seal element disposed between the gas chamber and the delivery outlet;
• and
• an opening mechanism configured, on reduction of the volume of the gas chamber to a predetermined volume, to open the seal element, whereupon a gas flow from the gas chamber acts to deliver substance from the delivery outlet;
• and
• an expansion mechanism configured to expand a cavity into which the device, in use, is inserted,
• wherein the device is configured such that application of an actuation force to the device causes an expansion of the expansion mechanism to expand the cavity and the device to deliver substance into the cavity.