Two different DNS benchmarking tools report slightly different results:
GRC's DNS benchmarking
tool was running in WINE. It reports that the Opal Telecom (TalkTalk) primary name server (184.108.40.206) provided by the peer during PPP session init, is overall fastest 
 an open source alternative to the GRC tool, reports the benchmarking results in more detail:
According to namebench
, the Opal nameserver (220.127.116.11) has the fastest individual response duration
However, on average, it is the ns8.bt.net nameserver (18.104.22.168) that is consistently fastest.
Hanging off that IP address, BT apparently runs Nomimum Vantio 22.214.171.124
, the carrier-grade DNS caching engine
Following close behind that BT name server is Google's Public DNS-2 server (126.96.36.199).
Although not really much to choose between any of the fastest servers!
namebench reported quite a number of failed responses or timeouts from the Opal primary nameserver, deciding eventually that it was "probably broken
". So maybe the Opal server is actually pretty fast but only while its load isn't heavy, at which point it just ignores requests?
Edited by asbokid (Sun 23-Jun-13 02:25:52)