EX7700 Extender is slow when using ethernet connection

I've had the EX7700 extender set up in conjunction with a BT broadband hub.  Via the Netgear hub manager I can see connection to the 2.4GHZ  and 5GHZ channels both of which seem to be used for wireless devices successfully.  I've now tried for the first time to connect a device via ethernet wired connection to Netgear.

Normally when connected directly to the main router this device will obtain download speeds of >40MB/sec.  However now when connected via the extender this device only achieves less that 10MB/sec.

Should the superfast web connectivity be available via the extender?  If so what Netgear settings do I need to change?  (Don't have built-in wireless in this device (PC) to check that performance via the extender.

Thanks for any feedback & suggestions.