Broken timing belt cog

I have never seen this before, I been working with cars for 25 years. I am building a large extension and had ran out of sand so I the 90 I bought was a none runner so I though I have a look. This is what I found broken crank pulley bolt and broken timing cog. I think who ever had this before tried to loosen the crank pulley with the engine starting and done this. It the only thing I can think off. Anyone got better idea?

Can not see that loosening off the crank pully bolt by any method would result in sort of damage. Is the shaft of the crank bolt still in the crank?

Possible your bolt has come loose and allowwed the keyway to frett inside the pulley wearing the slot away until its not strong enough?
Ive seen one really bad on a 200 years ago, but didnt split the pulley.

lynall said:

Possible your bolt has come loose and allowwed the keyway to frett inside the pulley wearing the slot away until its not strong enough?
Ive seen one really bad on a 200 years ago, but didnt split the pulley.

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Looking at the smooth fracture surface it looks like it has been a cracked there for a while, probably as a result of fretting at the keyway. Looks like the bits in the first post are not in the correct sequence (bottom and right bits should be swapped)?

No the bolt that holds the pulley on as well was snapped. It not getting fixed it getting a 200 tdi just posted to let people see . I never seen anything like that before