At the north-west corner of Lancaster House, near the ground now concreted for a car park, lies a sealed, ruinous, subterranean vault, and in that vault, as in some folk-tale about the secrets of the hills, there stands a riderless horse, with an attendant in an inner room a few paces away. It is nearly twenty years since he was visible to mortal eyes; the last living person known to have seen him is my colleague Mr. Arthur Trotman, who tried indeed to move him from his position, but was dissuaded. Not without reason, indeed, for an enemy land-mine had fallen in the neighbourhood and caused a considerable degree of damage, including the subsidence of the entire corner of the building. The sturdy frame of the horse was found to be actually supporting the roof and wall of the corridor in which he stood, and it was only too likely that further movement might bring down the vaulting on him and on those who had ventured to disturb him. Further investigation was discouraged, rubble and concrete were poured into the crater above, and the vault was left sealed and inaccessible beneath the newly created terra firma.