It looks to me that Tornado is coasting as there is no exhaust steam visible at the chimney. To avoid blowing off the fire door flap will be fully open and the dampers closed. That allows colder air over the fire rather than air drawn through the fire. . The light grey at the chimney top is when firing and shows the "Mixture" is correct. The very black smoke beloved by some photographers shows a very rich mixture which is very wasteful of coal and the firemans strength.Looks like the fireman needs some more training (no pun intended), he got too much air going through his firebox. Smoke should be light gray, not a blue haze.
The shots of Jeremy Clarkson on Top Gear were mainly for the camera as I never saw him putting coal in the back corners of the firebox. These LNER Pacifics have very wide fireboxes and there is a real knack to getting the back corners filled, if that is not done air is drawn through the thin patches and steam generation is reduced.















