nsd.nic.uk has no CNAME records.
Question and response
Question
dig nsd.nic.uk. NS
Answer
The response has no answer records.
Authority
nic.uk. 2846 SOA dns1.nic.uk. hostmaster.nic.uk. 1768318877 7200 300 2419200 172800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0