Having completed the mess that are the southern tube lines, we change at the nice new Canada Water station back on the the ELL, of which we got Shoreditch and Whitechapel earlier. Assuming everything goes to plan we have about 10 minutes to walk between New Cross Gate and New Cross at the bottom end of the line, and should just about have enough time to turn around at Shadwell between trains (if we miss the southbound train then we have a timetabled 6 minute wait, but I don't trust this line that much). Then we return to Canada Water through the Brunel tunnel and carry on up the Jubilee Line.
The tunnel was constructed originally as a foot tunnel by (among other people) Marc and Isembard Kingdom Brunel, however access was only via spiral staircases. Some years later a railway was constructed through the tunnel, which eventually became the East London Line. Plans are currently underway to extend the ELL to the North and South and eventually as part of those plans it will be returned to mainline rail operation and we won't have to worry about it when trying to do the Tube Challenge.
We've picked up all of our mising time on the northern, victoria, bakerloo and jubilee lines and are now back on course!