Milton Blockhouse was an artillery fortification constructed as part of Henry VIII's Device plan of 1539, in response to fears of an imminent invasion of England. It was built at Milton, near Gravesend in Kent at a strategic point along the River Thames, and was operational by 1540. Equipped with 30 pieces of artillery and a garrison of 12 men and a captain, it was probably a two-storey, D-shaped building, designed to prevent enemy ships from progressing further up the river or landing an invasion force. It was stripped of its artillery in 1553 and was demolished between 1557 and 1558; nothing remains of the building above ground, although archaeological investigations in the 1970s uncovered parts of the blockhouse's foundations.