The 1.1km connection tunnel, created at a depth of around 30m, will take sewage overflows from King George's Park into the main 25km tunnel at Carnwath Road, where it will be transferred to East London for treatment instead of polluting London's waterway.

Charlotte is one of the project's smaller tunnel boring machines (TBM), measuring 3m wide and more than 70m long and is named after suffragist Charlotte Despard. She was the first to break through the ground to complete a section of tunnel for London's new super sewer in October.

Having dug the 500m southern section of the Frogmore Connection Tunnel, from Dormay Street to King George's Park, she was then hoisted from the shaft, taken back to Dormay Street and put back into the ground to tunnel the final 600m to Carnwarth Road.

With the tunnelling now complete, Ciaran McQuaid, project manager shafts and tunnels, for the western section of the project said: "It's amazing to see Charlotte finally through into the Carnwath Road reception chamber and a big congratulations to the team for all their hard work.

"This will probably be the end of my 12-year connection with TBM Charlotte from being a shift engineer on her back in 2008 on the Thames Water Ring Main Extension, watching her going through her remanufacturing ready for tunnelling on Frogmore Connection Tunnel and then completing her job in style yesterday. For a TBM that is turning 26 in November and has now completed six tunnel projects, she did a great job."