Looks like a white trailer or seavan added to the Nanofactory site.
It's a 40' shipping container that first showed up on Google Earth in an image dated 3/3/19. It also looks like they drilled a series of holes next to it. Maybe those are the "foundation test pilings" they talked about in the 3/19/19 PR? If so, and if they are on the nanofactory site, that piece of dirt is a lot larger than shown in the Tech City map.
Also from the same PR:
The initially proposed 12,000 square foot facility has been expanded to cover 120,000 square feet
Interestingly, the area of the nanofactory site shown on the Tech City map is about 120,000 square feet. Maybe 120,000 never referred to the size of the building but rather the dirt? And that's why the 7/23/19 PR refers to the facility as only 75,000 square feet? If that's right, I don't think the container is on the nanofactory site but rather the site to the East.