 In 1553 , orders were issued for the artillery pieces to be removed from the blockhouse and taken to the Tower of London ; the fort was then demolished between 1557 and 1558 , the brick and stone from the site being reused to repair the Tower . The former site was probably rediscovered during excavations in 1826 , but was destroyed during the building of the Gravesend Canal Basin , Canal Road and the Gordon Pleasure Gardens later in the 19th century . Archaeological investigations between 1973 and 1978 uncovered the foundations of the blockhouse , now protected under UK law as a scheduled monument . 
