The Gravesend Blockhouse was one of five small forts built in 1539-40 on either side of the lower Thames to protect the river approaches to London against the possibile attack by an enemy fleet. It also defended the Gravesend to Tilbury Ferry crossing.This was part of Henry VIII's national programme of defence.  The Blockhouse was a D-Shaped brick tower with gun ports.

In the 1660's the Blockhouse establishment was enlarged to inclusde a residence for use of the Duke of York as Lord High Admiral. This then became quarters for the Blochouse Ordnance storekeeper and then later the Royal Clarendon hotel.

Charles II used the Blockhouse as a banqueting hall. then by the 18th Century, it has become a gunpowder storage magazine, before being demolished in 1844 to make way for the gardens of the Clarendon Royal Hotel.

All that remains of the Blockhouse today is the foundations excavated during the 1980s.