A British Transport Film classic showing the Elizabethan non-stop Express train from London to Newcastle and beyond.

When Gresley designed the walk thru tender which allowed a change of crews whilst on the move, he got his children to sit on chairs in single file as he measured the smallest dimensions they could pass thru comfortably whilst the tender still held 5000 gallons of water and nearly 9 tons of coal.
He thus enabled a crew who had rode up 'on-the-cushions' (9.04) to relieve the London crew who had taken it so far. If you notice the relieved driver at 11.08 is a true belt and braces man! classic stuff