This brought back memories, I thought just for a moment that the K2 locomotive in the picture had been shedded at Boston, we had several, then I recalled Colwick had them too, and more than us, they were used on the Skegness services in the summer mainly on freight all the year round. From what I can see of the signal box behind the train it is the standard GNR signalbox, and will have been there from when the line was first built. To get the details of the ground floor google a picture of Heckington Mill, it has the signalbox in the foreground, and is of identical type to the one at Trent Lane, though there may be minor variations of detail.