@Alexandre. Thanks for the reply. We have a very sensitive house guest at present who is working from home so I will try the experiment you requested when they have left and report back.

I have a mixed Deco mesh 3 x X55 and 1 x E4R. One X55 is the main Deco in the Study with other X55 in the Lounge and the E4R in the Integral Garage. There are ethernet backhauls from Study to Lounge...