Bluetail
I thought the Nimrod was trialled with 'dumb' bombs in 1982 with a view to giving it the capability to attack any naval shipping (principally the Argentine carrier) it might come across while carrying out its normal maritime role - rather than as a fall back option if the Vulcans had problems as you seem to imply. This was before the Nimrod had any SSM capability.
A bit of a suicidal option for Nimrod crews I would have thought, but there were lots of wacky ideas floating around then!!