These men were known to the security service - their names had come to their attention when they were investigating other plots over a number of years.
Michael Adebolajo was radical enough to try and get to Somalia to fight with al-Shabaab, and it seems there was MI5 contact with him when he returned.
On the other hand, there are thousands in the UK with similar radical views. They can't all be monitored. And although this was a savege, shocking attack - it was relatively unsophisticated.
Adebolajo bought knives in Argos the day before.
But at the end of this trial, after that bloody day in Woolwich in May, I think it is worth remembering not the murderers but Lee Rigby's family who sat through that harrowing evidence.
As they put it so movingly: They have justice but they don't have Lee back.