Originally called the Waterloo Barracks, and constructed in a castellated neo-gothic style, the building replaced the Grand Storehouse which was destroyed by fire in 1841. The foundation stone, laid by the Duke of Wellington in 1845, can be seen at the north-east end of the building. The name refers to Battle of Waterloo and the defeat of Napoleon in 1815. The cannons in front of the building were captured from the French at Waterloo.
The block is now used to house the Tower guard and, since 1967, the Jewel House.