Can anyone describe the symptoms that would be experienced should a turbo seize and stop spinning ?
How likely, or unlikely, is this to occur ?

Unlikely to occur BUT if it did, huge amounts of black smoke, way down on power, potential engine runaway if oil leaking into inlet, engine management light on, faults galore logged. BMW i3 Electric Car
2012 Full Fat RR 4.4 TDV8 (now gone)
2006 VW Touareg 3.0 TDi V6

My symptoms were. A little black smoke, hardly any which was surprising, lack of power to the point of absolutely no power before engine stalled, would completely refuse to start, engine sounded like a bag of bolts on crank. On inspection one turbo had completely seized up and the other had oil passing through and was on its way out too. Both turbos replaced and all happy 2009 (2010 MY) 5.0 Supercharged Autobiography
2007 TDV8 Vogue SE
2005 BMW E63 645ci
2024 Porsche Macan

Thanks for that, with the exception of the noisy “nuts & bolts” symptoms are similar to mine. I’m going to look down that route. Thanks again.

White smoke... oil burn