The answer may surprise you.

We all know the UK has internet blacklists managed by various agencies such as the IWF[1]. These blacklists are highly granular and allow blocking of individual HTTP resources.

Virgin is intercepting your DNS traffic and putting you through a proxy to Google. In this way they can block individual pages and images on Google without denying you access to the entire site.

UK ISPs are being forced by the law to filter certain content. Doing it in the manner detailed above angers their customers less. It also leads to interesting situations for site owners. If a site has even a single URL on the blacklist the entire UK will appear to be coming from a small set of proxy IP addresses.

[1] https://www.iwf.org.uk/

This is not correct. There is no law on the books in the UK which compels ISPs to filter content. There are a couple of court orders in place on some larger ISPs to block access to a few sites, however.

My apologies. Being unfamiliar with UK law I mistakenly made the assumption that the blacklisting is legally required.

However it might as well be. According to https://en.wikipedia.org/wiki/Internet_Watch_Foundation#Blac... it is in effect on 90%+ of UK ISPs and there is significant pressure on ISPs to implement this technology.

If that were true, they should just do what the law according to you says, and ban Google and other search engines. Let the customers then take their anger to those politicians responsible.

This is almost certainly a poorly implemented CDN.

They probably shouldn't be doing it at all, though. They're not known for great skill in maintaining a functioning network.

Does this still occur if you put your virgin media hub into modem mode and use your own router?

I'm using the "super" hub in modem mode and can confirm the same results on my network, even when using OpenDNS/Google DNS, although no DNSCrypt yet.