Originally Posted by
ATC Watcher
As far as I know at this time , no-one really know what caused the system to crash , the root cause I mean , not yet but likely by tomorrow or in the next coming days we'll know
I'm a little confused by what you say. As mentioned upthread, it appears that the issue was a corrupt message from IFPS that the local (NATS) automated flight plan processing system couldn't reconcile. So it fell over. Without automated processing of flight plan data the NATS systems can't distribute flight data to the required sectors thus manual reversion and manual processing of flight plans is required.
Clearly, why a single point of failure has such an impact is a reasonable question, especially as several similar events have previously occurred (google for public domain examples of investigations). One hopes that e.g. a corrupt datalink message to an A350 wouldn't cause reversion to manual operation.