There are flats, they are on one side of the spindle only though so I will mill a corresponding flat opposite and make sure I can get a good spanner across them.
IIRC it's the flat would have been for the grubscrew to hold the original pulleys onto the shaft.
I think I just used a set of molegrips to remove the chuck when I had one. Bit crude, but it worked, although I rarely had any reason to remove the chuck from mine.
Although it has reminded me, I reamed my spindle out so I could fit 16mm bar through it, instead of the stock 5/8" bore.
I have decided t to a bit every single day, that way it will get done sooner rather than later, mounted the drives today and installed an on/off switch: