NatWest have stated that they are working on the issue, and claim that the online system is working.
However, having had several unsuccessful attempts to login and access the payments section, I tried to transfer money from one account to another and whilst the money was debited from one it has not been credited to another.@muppetwho Hi, we are currently investigating reports of this issue. Online Banking is still available. Thanks for your patience. LB— NatWest (@NatWest_Help) April 28, 2017