The construction of the 504m tunnel was designed to help those living in South London who worked in the docks and the tunnel owes much to the efforts of working-class politician Will Crooks who had worked in the docks and chaired the London County Council's Bridges Committee, who were responsible for the tunnel. Crooks would later serve as MP for Woolwich.
The tunnel was designed by Sir Maurice Fitzmaurice and built by Walter Scott & Middleton and opened on Saturday 26th October 1912. Now made partly redundant by the Woolwich Free Ferry and the new DLR extension, it is still the only way to cross the river here for free at night time, and that is possibly why installation of new CCTV and communication facilities, as well as reduction in leakage and new lifts, are so important. Improvements are scheduled to be completed by March 2011.
For more, see http://www.greenwich.gov.uk/Greenwich/Travel/foot-tunnels.htm