Some video of the 125 Group's excellent Class 41 prototype HST powercar which they brought along with their trio of Mark 3 coaches. This was my first time riding behind any Paxman Valenta-engined powercar and it is impressively loud - no video truly does these things justice IMO.
In fact, I had to edit the video down more than I would have liked because the turbo scream on full chat tends to overwhelm the microphone in my old camcorder (the mics in my newer HD cams are utterly terrible for wind noise, even worse than this, so I don't use them for on-train recording).
Still, I hope you get some enjoyment out of this.