After a considerable period of time, and a great deal of inconvenience to those who live alongside Boundary Brook, we have received this promising message from Thames Water:

In terms of progress, the whole house misconnection in New High Street
consisting of 13 separate misconnected appliances has now been dye tested
to confirm correct rectification to foul.  More significantly, further
investigations have taken place at Manor Hospital and the flow monitoring
has confirmed that the surface water discharges from their storage tank do
correspond to the high flows experienced in the open culvert in Brookside.
However, whilst the connection of this tank to the surface water system is
in accordance with normal practice, our further investigative survey work
has lead us to believe that some of the flats behind the hospital are
misconnected into this tank rather than the foul sewer. A meeting with the
Hospital has taken place to explain our findings and appraise them of their
responsibilities for the private drainage on their site.  As the flats
drain to the sites private sewer it is the Hospital’s responsibility to
ensure the appropriate Housing Association rectify the misconnections. This
is now being pursued by the Hospital who are thus far cooperating fully. I
would just add that whilst our investigations to date have found evidence
of domestic sewage misconnection from the flats, we have not found any
evidence of misconnection at the hospital itself .

We are delighted that the hospital is giving full co-operation in trying to ensure the housing association sorts out the problems in the flats.  We shall keep you posted of further developments and continue to press hard for as speedy a resolution as possible