And now as far as I've got. As the toe has split I decided to remove the scuff sheet to see how bad the blade was.
The heartwood is looking like crazy paving with cracks and wobbly bits of willow
There appears to be some delimitation in the middle (not seen in the photo), and there's a corner fallen off!
All in all this one may be beyond repair now.
I'll speak to the owner tonight about how (or if) he wants me to proceed, and update this thread when I know what's happening