The great and the good rarely, if ever, accomplish all they wish to achieve without the able assistance of many skilled men and women. To have a very capable person beside you acting as guide, confidant and adviser is essential. Even better when it is someone with a depth of knowledge equal to, or even better than your own. If all these skills can be combined in one trusted, assistant so much the better. To a leader such a person may be valued 'beyond rubies', because they have the ability to take ideas, add something and help make them a reality. For Herbert Nigel Gresley, CME of the LNER, Bert Spencer was just such a man. As Gresley triumphed his faithful, introverted and highly talented assistant remained resolutely in the background playing an unsung yet key role in the development of Gresley's outstanding Pacifics and his many other memorable locomotives. For sixteen vibrant years Spencer sat beside his greatly admired leader witnessing and participating in all that happened adding much to an emerging legend that still resounds with us today. Here, for the first time, is Spencer's fascinating story, much of it in his own words. This was made possible by the thoughts and memories he recorded in letters to friends, papers he wrote for the Institution of Locomotive Engineers, official documents and much more. All this has been edited together to produce a unique and important personal narrative of his life and work.