My money is on a major backend upgrade gone foobar and somehow foobarring the rollback (if they even considered rollbacki?!?!?!). Either that or their prod is completely hosed somehow (fire etc.) and they've had to switch on their never properly tested, not properly built or scoped DR that was just put in to tick some audit by a non IT person putting a check next to a box.
A break-fix does not take 5 days to resolve, not even a large SAN.
I've seen some rank amateurish behaviour by enterprises with multi million dollar turnovers so its no surprise for a monopolist vendor like Pearson to sit there and watch the money roll in. Unless there is some kind of legal/contractual or PR ramification from downtime mgt just don't get it until it happens.