Usually we find out ahead of time if there's to be some disruption to the network due to Sony's engineers giving the PSN a prod and a poke, but it seems this latest check-up has come out of the blue. Strangely enough, today is also the day that DriveClub got a new update – coincidence?
The official PSN status page doesn't mention any problems, so maybe it's not expected to last too long. Fear not, though, we're here to keep you updated and we will when more information becomes available.
Update (13:45PM BST): Sony Europe employee Chris Owen has said that the company's investigating the current issue: "We're aware that there are currently issues with PSN; we're investigating the issue. We'll keep you updated regularly with any progress."
Update (14:00PM BST): We're able to connect to the PSN here at Push Square Towers, so it looks like service is slowly being restored. We'll keep you updated regarding any potential setbacks.