About two hours ago, I submitted an incomplete census return -- it looks as if some keystroke produces an immediate submission, at least on my browser. I'll be submitting a complete one later today. Yvain, if you want to suppress the incomplete one and need help in identifying it then I can help. I was partway through the calibration questions when I accidentally submitted.

(I see TrE had the same problem.)

[EDITED to add: Complete return now submitted.]