This resulted in the boring machine getting stuck and reported to being abandoned under Streatham Woods.
My approximation of the location marked on the attached map - courtesy Friends of Tooting Common.
The initial ring was constructed by Thames Water between 1988 and 1993. Two extensions have been constructed, and there are plans for further extensions through to 2025
(Engineering Timelines http://engineering-timelines.com/.../engineeringItem.asp...)