Tens of thousands of tourists visit Whitehall each year and gaze at the Horse Guards sentries, but the history behind Horse Guards, and the sentries in front of it are known to virtually no-one. This is the first book to tell the absorbing story of a site which has been used for martial activity continuously since the mid-16th century. From knights competing to be Champion of the Tilt during the reign of Henry VIII, to becoming the first War office, to its role today, the building has continually played a military role. Written by an expert who has researched the building for more than 40 years, this fascinating book tells the hidden history of one of Britain's most famous landmarks.