[spoilers] Lucas. Just Lucas.

[HellsBells]

I loved that scene in 7.3 with Lucas and Jo in the surveillance van. You are absolutely right, binkie how quickly Lucas picks up on Jo's concern for Ben. If I remember correctly he initially tries to make light of the situation with the words 'we learn by doing' (sorry that may not be the exactly words) but then corrects himself and assures Jo that Ben will be fine and Lucas will look out for him, and Jo takes comfort from those words.
I always thought his initial statement of 'we learn by doing' rather harsh and uncharacteristic for Lucas and maybe an indication of the state of mind he had to adopt while in prison.