A recent Windows 10 update left many users with slow WiFi; connecting on a LAN cable showed significant speed difference compared to WiFi (only running at 20% of normal!)
Cause: the June 2017 Windows 10 update was indeed an improvement, enhancing and strengthening WiFi components. Sadly many WiFi adapter manufacturers have still not released updated WiFi adapter drivers, and many of the existing drivers do not work well with the new version of Windows 10.
We recommend users download and install this interim update, which compensates for the existence of "old" WiFi drivers, effectively using the "old" Windows 10 modules where "old" WiFi drivers are detected: http://www.catalog.update.microsoft.com/Search.aspx?q=kb4022716
Download the 700+MB file and install on Windows 10 devices; average install time = 15 minutes.
A future release version of Windows 10 will include this hot fix, whilst we stil wait (and wait) for WiFi manufacturers to release their updated drivers...