Tried Mark Ferguson's fix certainly worked but introduced a 3 minute delay during booting. Leaving router up powered down ubuntu 20 times back every time.
Then I undid the changes to etc/udev/rules.d/85-ifupdown.rules putting the == back. The 3 minute delay disappeared but the problem did not come back either. Again powered up and down 20 times with no loss of network.
Using usb WiFi
Now totally confused
Tried Mark Ferguson's fix certainly worked but introduced a 3 minute delay during booting. Leaving router up powered down ubuntu 20 times back every time.
Then I undid the changes to etc/udev/ rules.d/ 85-ifupdown. rules putting the == back. The 3 minute delay disappeared but the problem did not come back either. Again powered up and down 20 times with no loss of network.