Overnight, my temporary mast for the big-wheel collapsed: it was simply resting against the guttering and blew over crushing one of the clover leaves. Hopefully, I can bend this element correctly again. I shall do this shortly.
UPDATE 1414z: Averted! I managed to straighten out the bent clover leaf, re-erect the antenna (briefly) and re-test. As far as I can tell, it is the same as before now.