Thanks Grahameo, as it happens, I decided to email the video to my mechanic, he immediately suggested i come in.. So, after the exact inpection you just recommended, we found it to be the cam belt tensioner.
So, I booked it in for next month for a cam belt kit (albeit only half way through its service life) - sorted, or so I thought....
He had to take the aux belt off to eliminate that as a source, as you suggested, but he didnt put it back on properly....
Just a few miles down the road a faint smell of burning rubber, then a thwat thwat thwat sound.. stopped the car.. yep there was a noise there alright.. so did a u-turn to go back and then - bang and a almighty knocking noise, followed by loss of power steering, alternater and then silence.
Well, the engine still ran, just the belt had shred its self to oblivion so as you would expect, silence
Anyway, returned to mechanic, checked the engine, turns out the failed aux belt took out the cam belt. So, he's replacing the cam belt for me tonight.. car will be ready in the morning
Poor bugger is working through the night for me.. boo hoo.
Mind - I had a feeling it was related to the cam belt, so I'm glad its getting done now so I don't have to risk blowing the engine up over Christmas.. I already did that 2 Christmas's ago.
Moral of the story, always make sure your car has an engine undertray.. seems they are good for something - keeping the muck and crap out of the pully systems. Mines never had one, which is why I've had 2 x premature cam belt failures.. well one full failure, and one near failure.
Second moral of the story, encourage mechanic to put your car back together properly.
I'd be bored if i owned a toyota.