ns4.virtual1.co.uk has no CNAME records.
Question and response
Question
dig ns4.virtual1.co.uk. NS
Answer
The response has no answer records.
Authority
virtual1.co.uk. 1565 SOA ns3.virtual1.com. hostmaster.virtual1.com. 2019040737 14400 1800 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0