Bridgeport knee assistance required

After much arm wrenching I am going to fit an Z-axis power drive to
Bridgeport. The make is "Align" and the instructions seem quite easy
to follow.

However, I have started to strip the elevating crank assembly and I am
now stuck. The castle drive sleeve has been removed. I have the dial
holder to remove next. It unscrews ok but there is a key in the shaft
which is preventing me from removing it. The key is inside the bore of
the dial holder and is not easy to get at. Sadly, the key is not loose
but I need to remove it to get the dial holder off. The parts diagram
shows no other fixings at this point.

Am I missing a trick here or do I just have to try and flatten the key
and then pick up the front edge to remove it?

As a number of us have BP's I hope someone can assist me.

Regards

David