Police said they believe the recovery of a rocket launcher "has saved lives".
The Police Service for Northern Ireland has has been on high alert after a series of attempts by republican dissidents to kill members of the security forces.
These weapon systems are clearly intended to kill and we should be in no doubt that the recovery of these items has saved lives.
More top news
The PM will sound out the possibility of new free trade agreements with Gulf states for once the UK has left the EU.
In the unexpected announcement on Monday, Mr Key said it was the "right time" to leave politics.
As the Government's Brexit appeal comes to the Supreme Court, here's a look at what you need to know.