Spread a thin layer of the damson jam on one long edge of a piece of lemon sponge cake and sandwich together with a piece of pink sponge. Repeat this process with another strip of lemon and pink sponge. Place 1 pair of jammed sponges on a board so they are flat. Spread a little more jam over the top, then place the other strip of jammed sponge on top so the sponge colours are alternated forming an oblong loaf. Repeat this process with the remaining sponge.