One down, two to go.
That was physically - and psychologically - more difficult than I expected. My plan was to used our camping bog, temporarily lifting the "no solids" rule, but I firstly found that my enormous arse would not fit comfortably on its little seat in such a way that it would tidily collect everything that I might produce, simultaneously from both sources, as it were. Secondly, it is only a heavy duty plastic bucket and I had concerns that my elephantine mass might cause it to break.
Plan B. A double layer of paper handkerchief (man-size, naturally - much less flimsy, and of course a considerably greater area than a few sheets of bog roll) over your hand and wait for the first instalment. It's actually quite hard to steel yourself to catch your own turds, so conditioned are we from an early age not to do so. However, I collected a walnut-sized piece, used cardboard stick number one to smear a little in Window 1 of the test kit, disposed of the unwanted debris down the bog, waited for the second turd and repeated. Each test kit allows for three different craps and you have to take two samples from each, at different stages of the bowel motion, I suppose to check that different bits of the rectum are free from cancer cells.
The necessary deposits are now safely stored in my bedside cabinet, with the little flap tucked into its tab, waiting for the next two instalments. The cardboard sticks have been disposed of in a dog-shit bag to be exported to the park when we go later this morning.