The old greenhouse measured 24x12ft, and crossed almost the entire plot, East to West, which is why there's no central path, and to get from one end to the other one had to skirt the greenhouse, with hardly room to get a barrow around. When there was a greenhouse there, it must have looked a bit odd, but at least it was doing a job. Maybe it was kept by a family that loved tomatoes. Or "Indian hemp".
The time has come, and it's worse than I'd feared: it's not only stray bricks and a forgotten path (down the middle of the greenhouse, obviously), there's a proper brick greenhouse foundation wall, properly mortared and laid on top of rubble - a real pro job.
In the photo you can see it on the NW side. The top of the wall is slightly less than one spit down from the current surface, and I briefly thought of leaving it alone. But the surface in this area is higher than the rest of the plot. The foundation-wall has retained earth, whilst the rest of the plot has been allowed to sink away and be hollowed out. If I'm to get nice level beds, it has to go.
Which is going to keep me out of mischief. A 24x12ft area means 72ft of boundary/foundation wall in total. I need to dig down first to the top of the wall, and then one spit either side of it; (the soil down there isn't great, clay mixed with bits of rubble and the ubiquitous broken glass). And then knock out the bricks with a hammer, and throw on them onto The Frogs' Winter Palace. I tried one brick last night, and it started to fragment under the hammer - the mortar is in better condition than the bricks.
Dad and another allotmenting pal have suggested work arounds, making it into a raised bed or gardening over it but I'm not having it. First, raised beds, don't get me started. And second, it's buggering up my levels if I try to go over it, big mound right in the middle of the garden. No. It's going. Massive greenhouse right across the middle of the plot? Bloody daft idea in the first place.