The drain outside nos. 75-83 that had caused the excessive flooding has been unblocked this lunchtime.
It appears that concrete had been poured into the drainage system (probably from building works further along the street) and had trickled down, underground, to come to rest and set here at the lowest point, thereby blocking the pipes.
If anyone employs or sees contractors using concrete, please warn them not to unload unwanted concrete into our drains!
I am thanking Cllr Jim Dickson, whose intervention last week undoubtedly speeded things up.