Rescued desk made by Preston Ltd.

I rescued this desk from being thrown out at an Armoury. They said I could have it! It's marked up by a number of users, perhaps going back decades. The armoury existed in WWI. What I'd like to know is when this desk may have been made. It's a wood structure with wood veneer sides and top (these need replacing). The hardware impressed me: inside the left drawer are heavy duty springs attached to to shelf, for the typewriter perhaps? And wood sliding on wood, beats anything they make today. If anyone can tell me more about it, I love the back stories to old items. Thanks.