The museum of Docklands tells the history of the Thames and the docklands area from early Roman times until the present. I'd gone to see an exhibition of photos and film about the Thames Estuary but also took in the rest of the museum which is fascinating.
The museum is set in an old warehouse that once would have formed a working part of the docks. There is an extensive collection of artefacts from the working docks. On one of the floors you step back in time and wander through cobblestone streets with replica stores creating the ambiance of a previous time.
Worth the trip and entry is free.