Here's what the work looks like at present:
Four feet beyond that back wall is where my computer is. The plumber also took up the carpet and two planks from the floor so he could access some pipes that he divined were there. In order to enable this, I had to move a bookcase full of books last night. Surprisingly, you can't tell just by looking which one of my big toes I dropped this on while relocating it in front of my other bookcase.
The waste pipe for the toilet was embedded in concrete. The plumber had a go at removing this yesterday but failed to make an impact, so this morning showed up with a breaker he'd hired for £25 and took it on again. This time, he succeeded. He did it without wearing ear defenders. I put my headphones on as a form of protection, but I don't know how effective they were. Strangely, this wasn't the noisiest it got: when he was cutting through the floorboards it was worse. There were vibrations, too, which I could feel through the soles of my feet. They were so bad that my computer mouse picked them up and moved of its own accord. This continued even when there was a respite in the sawing; I don't know if it was the mouse regaining equilibrium or my hand still shaking.
He's packing up now, so I expect he's done. He'll be back when we've had the walls plastered and tiled.
Oh, if you're wondering about COVID-19 precautions, he assured us we were OK because he'd put us in his bubble for these two days.