To make the pesto put the watercress, parmesan, cashew nuts, and salt into a food processor and whiz into a paste.
Transfer to a container and mix as much olive oil as you want to taste.
Line a sheet pan with foil and bacon until done, turning halfway through. Drain on a paper towel and set aside.
Assemble your sandwiches starting with the sandwich base, then pesto, bacon, peppers, sundried tomatoes, radishes, rocket arugula, radish sprouts, and sandwich top.