2010 XC90 D5 - stopped with a small puff of smoke from under the bonnet

[kirksterno1]

Thanks for adding me.
I have a 2010 XC90 D5 which was making a ticking sound when I was on a weekend away. Whilst I was driving it home, which I shouldn't have, the car stopped with a small puff of smoke from under the bonnet. I looked under the bonnet and there was a small piece of belt. I assumed it may have been a pulley. My mechanic and I looked at it yesterday. It won't start, but when I turn it over with the key all the pulleys turn. I assume the bottom ends ok. We checked top dead centre on the timing belt but couldn't see the lower mark. Haven't taken the wheel off to check. Will do a compression test to see if a cylinder is gone... Hoping they're ok. If that's all good, does anyone have any idea what it may be and what else it could be? I bought it new and it's been a great car. Cheers Julian

Below is the video I shot prior to it stopping...