Place cream cheese, lemon zest and dill into food processor and blend until ingredients are incorporated.
Lay out slices of bread and spread cream cheese mixture on all four slices, avoiding the edges. Place cucumber slices on top of each of the slices of bread. Top two of the slices of bread with watercress. Place other piece of bread with cucumbers on top of slice with watercress.
Cut all the crust (edges) off of the bread so bread is crust-less. Slice bread diagonally into a triangle and slice triangle in half.
Recipe by Tout va bien! (tm) at https://christymajors.com/downton-sundays-the-carson/