The following memory was provided in response to a social media post featuring the Hellifield coal stage and Jamie has kindly given us permission to quote it here:
I remember watching Locos being coaled there while changing trains as a boy. The coal was shovelled into special little tubs that ran on rails at right angles to the wagon. The rails had ends that curved up at right angles so that the tubs tipped over and the coal went into the tender but the tub stayed on the stage.
We've not yet managed to obtain any photographs showing this process in operation at Hellifield, but the coal stage at the Didcot Railway Centre operates in a similar fashion and the following page from its website includes two photographs that are espcially informative:
https://didcotrailwaycentre.org.uk/article.php/425/the-coal-stage