Combine all the vegetables and watermelon in a large mixing bowl and process with a hand held blender (a standard blender will also work).
Taste and add salt and pepper and 2 tablespoons of olive oil.
If the texture of the gazpacho seems thin to you, add some fresh bread crumbs to thicken it up.
The gazpacho can be strained if there are a lot of seeds and bits of chopped up veg.