Cap stone on the school wall

This is a section of the school wall that still stands, at the very far end of the upper playground beyond the "Dubs". Notice the name of the manufacturer and the date on the capping stones. Every half dozen or so of the cap stones on the wall carried this inscription. The clock tower still stands, just, and can be seen above the wall. 
The weed on the wall is an American willowherb, Epilobium ciliatum, first recorded in the UK in the 1890's and now one of our most common weeds of waste places (one of us did Botany at A-level!)