He considered various plans, but he felt the best choice was to copy the prison key. De Valera used his background in mathematics to geometrically copy the chaplain's key in wax during mass, and he used his knowledge of projective geometry to copy this to paper. When the copied key, delivered in a cake made of plaster Paris, came it was found to be too small. De Valera then compared it with the drawing they had of the key, and it fitted perfectly. His mathematician's mind was not long in figuring out the problem. He had allowed the wax to harden while still in the plug tobacco box with the result that in the shrinkage caused by the cooling of the wax the impression became uniformly smaller than the original key.' A copy of the key, which fitted the locks, was eventually made, and de Valera, accompanied by others, escaped on 3rd February 1919.

Article by: Cáit Ní Shúilleabháin, University of Cork, caitnishuilleabhain@gmail.com