The eagle-eyed amongst us may have noticed one of several rather crude yellow signs as illustrated; unusually, they have no attribution, so there's no-one obvious to turn to for more information. I'm surprised and disappointed that no-one appears to have consulted, or even notified any residents in advance.
My thanks to the Foxley Residents' Association who have found out that Higher Drive will be closed to through traffic near 90A Higher Drive for some sewer works, probably arranged by Thames Water.
As local residents will know, there are no easy alternative routes, so I regret that it will be a long drive round this obstruction; this is why the works are scheduled for the quieter traffic season.