Having owned an xk140 o.t.s, I can definitely agree that this is exactly how a roadster should sound, mine was sorted for racing at Goodwood which made it a bit more difficult for driving on the road but like most cars with an XK engine, it was brilliant.
Very nice. What is the light on the dash and the switch on the steering wheel. The light comes on about 4 minutes ito the video, the passenger (owner) points at it and the driver moves a lever on the steering wheel.
As best I can remember the indicator switch in the centre of the steering wheel which was the norm of that era on many vehicles, and similarly the light on the dash is a reminder that the indicators have been selected on.
OK, that makes sense, the owner was just pointing out that the indicator was on and then the driver turned it off. Now I re-watch it you can see him turn it on about 3:30 just before a corner.
Honestly I would be checking the exhaust system because that car doesnt sound right to me. I did wonder if it had a blow. Its too uneven a beat for an in line 6 IMO.