The RSPB’s Rainham Marshes reserve has kept rather a lot of World War I heritage.

Amid its reedbeds and walkways is a stubby, circular tower, just in the shadow of the River Thames’ flood bank. During World War I this was used as a lookout post from which soldiers would scan the estuary for enemy submarines attempting to sneak up the Thames. It seems too short for the job, but the embankment was much lower 100 years ago than it is today.

Legend has it that, in 1916, a machine gun, mounted on the top of this tower, helped to shoot down the German zeppelin LZ15 as it made its way towards London.

A mural of that engagement is one of several that adorns the remains of a steel-lined earthwork at one end of the reserve. Backed by several feet of earth, this was where soldiers lifted up paper targets on long, wooden poles to be shot at by their comrades at the other end of the range.

Original numbers at the surviving butts, Rainham Marshes

A segment of the butts still stands, with tall numbers, a bit like those on a running track, still standing proud against the skyline. Nearby, the digits recur atop a purpose-built hide that affords superb views of the wetlands.

The railway line that once brought troops here today carries Eurostar services that thunder past the edge of the reserve, seemingly without concerning the wildlife. Somehow, though, the presence of the trains does not make the marshes feel any less remote and the haunting cry of a curlew, drifting in from the estuary, only adds to that feeling of mystery and isolation.

That feeling was perhaps shared by the troops who were based here during World War I, among them, in 1914, soldiers from the 18th (Eastern) Division, who lived under canvas until huts were built as the winter set in.

Water fills the area where troops would have raised targets above the bank