Locate the two screws that hold the case together. Unscrew them (philips 1)

Using relatively much force, insert two fingers beneath the casing and pull it off from the counter part. It is held in place by few plastic clips that will yield with force without breaking (in my case, where I was destroying it)

The clips are located relatively close to the upper edge of the casing, if you are interested in shimmying them with a palette knife etc.

You are left with the top most cover off, the power cord holding it still in place