 But Engel also kept up correspondence with colleagues from Germany and followed trends there.Engel's relationship with key Prussian architect Karl Friedrich Schinkel, three years his senior and both having studied at the Bauakademie in Berlin, has yet to be properly verified.The influences from central Europe would also take on board a more formulaic process, typified by standardisations of design formulas in post-revolutionary France by Jean-Nicolas-Louis Durand, for instance by the use of design grids.