The star in The Railway Children was not Jenny Agutter, though in 1968 when she first played the role of Roberta Faraday I was far more interested in other things than to take note of “girls”.

In the 1970 film version, though distracted by the setting, I was only interested in the steam loco that appeared in the film alongside the children.

It was a GWR pannier tank 0-6-0 5700 class and this one in particular, no 5775, was built in Swindon in 1929.

In the film it appeared in a brown livery with the GN & SR emblazoned on its water tanks.

It was such a shame, as they always look resplendent when painted green with GWR picked out on the water tank sides.

This was a superior little shunting engine and general dogsbody, some were fitted to run the auto coach trains and soon they spread across the country.

Originally introduced as a replacement for the William Dean 2021 Class, Collett improved the design and more than 860 were built, which ranks it second in the most produced loco league table.

It was quite a feat for Swindon. However, Swindon did not build all of them, 275 were built elsewhere by private contractors.

I am told that the ones built at Swindon always stood out head and shoulders above the others!

They were known as Ducks, because they waddled as they moved along the track, due to the water in the tanks sloshing from side to side on a high centre of gravity. Duck is the name given to one of the characters in Thomas the Tank Engine stories, because of the waddle.

Although laughed at, it had the last laugh as it outlasted many of its bigger cousins, such as Kings and Castles, and continued working long after steam on British Rail finished.

The London Transport Executive had a fleet of panniers and used them on the Hammersmith and City lines, running in and out of Paddington.

This fleet was fitted with condensers to ensure that the exhaust steam would condense back into the water tanks and, with special modifications to their brakes, this fleet was in daily operation carrying out shunting duties into the early 1970s, when they were replaced by diesels.

Some even continued long after this date as colliery locos working for the National Coal Board in Wales, possibly right into the early 1980s.

I recall seeing Ducks at work in the northwest as a youngster and, even when painted black, they were still a sight to behold, a sort of GWR novelty amongst the Midland Region Locos.

A handful of the 800produced have made it into preservation and there is one exhibited at Steam, no 9400, but some are still waddling about on various heritage railways up and down the country.