The site in question is charts.dft.gov.uk (VERY NSFW). It resolves to the CNAME charts.dft.gov.uk.s3-website-eu-west-1.amazonaws.com, which is quite clearly hosting a porn site of some kind.
I suppose there's a few possible explanations here: (1) the original site was hosted on S3, and at some point the bucket was dropped and someone else picked it up, (2) it was originally hosted on S3 and the bucket got hacked, (3) someone with access to the DNS has decided to go rogue and point it at a somewhat-legit-looking but fake domain. If there are historical DNS records floating around it might help to narrow down what happened here.
I don't think it was #3: Amazon owns and resolves it for amazonaws.com. If you could hack that, you could do much more serious damage. I'm assuming it's #1. Bucket names are global.
1. gov.uk’s DNS server used to point charts.dft.gov.uk to something legitimate
2. Someone hacked gov.uk’s DNS server, and changed this one specific domain to CNAME charts.dft.gov.uk.s3-website-eu-west-1.amazonaws.com
3. That same someone set up their porn thing at AWS in a bucket that maps to charts.dft.gov.uk.s3-website-eu-west-1.amazonaws.com
But why such a specific bucket name? Perhaps the perpetrator did it because he knows how the gov.uk DNS is maintained, but then it would be an inside job. If only the process were as tight and clean as in peppa pig land!
I followed few links there and it’s not even a porn site, it just a shallow catalogue of {img-ahref -> img-ahref} which tricks you into “/dating.html” which redirects to some “dating” site. Probably just a SEO bs.
I suppose there's a few possible explanations here: (1) the original site was hosted on S3, and at some point the bucket was dropped and someone else picked it up, (2) it was originally hosted on S3 and the bucket got hacked, (3) someone with access to the DNS has decided to go rogue and point it at a somewhat-legit-looking but fake domain. If there are historical DNS records floating around it might help to narrow down what happened here.