Wolf & Wolf v Forfar Potato Co 1984

What happened

FPC's offer to W to sell potatoes was for acceptance by 5pm.
W issued a qualified acceptance which was rejected by FPC
W then accepted the original offer - all before 5pm; FPC ignored this and so W sued for breach of contract

Significance

while the first offer that Forfar Potato Co. proposed was valid, it became invalid once Wolf and Wolf added additional conditions to it. Thekey wording in their response to the offer was "but". This was seen as a counter-offer, By proposing a counter-offer, Wolf and Wolf had consequently refused the original offer meaning that it was invalid could no longer be accepted
There was never an agreement reached between them because both parties kept adding additional conditions. Once new conditions were put in place the previous agreement became invalid and could no longer be accepted. This was a reoccurring cycle. As a result, the existing offer was no.