GWR Large Prairie 5199 having a drink with the help of footplate crew and station staff. It was a surprise to se the loco arrive light engine from Carrog so maybe it was an emergency top up. Given the amount of steam this was producing out of the chimney (as seen in other gala photographs) maybe it was unplanned. Once topped up it headed back to Carrog to take up its duties whilst the station staff swept the platform of excess water from overspill and a leaky pipe.
Looking at other gala photos uploaded it did there same on the Saturday schedule so it was planned.
Uploaded to Flickr by ARG_Flickr on 18 October 2017