During the second half of the 19th Century the Thames Estuary had been heavily defended with more than nine coastal defence installations. The London docks were the epicentre of the various commercial ports spread out of the British Empire. Coastal defence batteries were built on both the north and south side of the River Thames. These included:
- New Tavern Fort
- Tilbury Fort
- East Tilbury Battery
- Fort Coalhouse was built between 1861 and 1872 with one level of casemated positions for seventeen guns. Between 1901 and 1903 positions were made for four 6-icnh Mark VII guns on the casemate roof.
- Fort Coalhouse 6-pdr QF Battery
- Cliffe Fort
- Slough Fort was built between 1861 and 1869 with two wing batteries, each of two guns, being built between 1889 and 1891. In 1907 the right Wing Battery was remodeled to mount two 9.2-inch Mark X guns.
- Lower Hope Battery built at Lower Hope Point in 1898 with two 12-pdr QF guns and supporting searchlights.
By 1905 the Admiralty view was that any attacking ships would have to pass the Medway Defences around Chatham and Sheerness before they could reach the London Docks. This was considered highly unlikely, and the Thames was graded as a Class C Port. The Committee on Armaments of Home Ports (TNA CAB 16.1) recommended in 1905 that only the four 6-inch BL Mark VII guns at Coalhouse Fort be retained. They also recommended that the three searchlights at Coalhouse Fort be modified to act as fighting lights. In 1905 the defences are shown as: