Suddenly all four of my computers began to play up. Became very slow and refused to connect to the Internet
To my surprise all of the Android devices continued to function completely normally
Quite a lot of head banging but finally a solution
All of the computers run Windows 10 with Mcafee Total Protection
Mcafee was the problem !!
Answer discovered at
So – go to Services and both “ Stop “ and “ Disable “ Client Analytic Service
Seems to solve the problem – though I think we are still waiting for formal information from Mcafee