Rare footage of the North British Railway H class

I found this footage from Decades Of Steam: The 1920s.

[@LneR-PrOdUcTioNs]

How can you find of decades of steams 1920s full version?
I can't even find one.

[@awesome-xk8vj]

How did you get these rare footages of the engine's? Please respond when you get this please.

[@gresleyng-thebritishrailwayfan]

Look in the description. I found it on The Decades Of Steam the 1920s.