While the UK government might still be checking systems, it seems that LulzSec themselves have denied hacking the UK census.
A recent Twat from LulzSec's Twitter feed said: "Not sure we claimed to hack the UK census or where that rumour started, but we assume it's because people are stupider than you and I."
This is followed by: "I'm not seeing "we hacked the UK census" on our twitter feed or website... why does the media believe we hacked the UK census?"
A previous message noted: "Seems the glorious leader of LulzSec got arrested, it's all over now... wait... we're all still here! Which poor bastard did they take down?"
A 19-year-old man was arrested in Essex earlier today.
A PasteBin note earlier today appeared to suggest the collective had grabbed UK census data.
But as LulzSec notes - "anyone can cut and paste the Lulz Boat ASCII art and general lighthearted theme."