Despite its somewhat frightening appearance, this is a harmless (to people) European Garden Spider, Araneus diadematus.
Julian spotted it hanging down past the open kitchen window. “Dad,” he came running, “you’ve got to photograph this spider from the kitchen window!”
I used my 200mm Nikon macro with a 6T close-up filter, and the macro strobe rig on a ring at the end of this rather long and heavy lens. The red in the background is from a begonia in a hanging basket. I processed the image three times from the RAW, once for the body of the spider, once (in a darker exposure) to control the highlights from flash reflection on the spider, and in a lighter exposure to bring out the colors in the red begonia.