I've removed the seat belt tensioner/roll on the drivers side (LHD) to get to the fuel pump.
When I was on my way to put it back, I realized that the belt had rolled all the way back in and "locked"...

I've can see the mechanism that stops the belt from rolling out, but I can't find out how to release it.
Does anyone have a clue how to do this?
All the way in:

Locking mechanism:
