From Tabtravellers recounting of the conversation at checkin, it would appear that the fact it was Cava was key which then led the checkin agent to justify refusal to carry it by saying it was dangerous and might explode. Clearly, the checkin agent was wrong and as a consequence TabTraveller is short two cases of cava at a cost of €300. I see no reason why TabTraveller should not ask BA to recompense €300 for the checkin agents mistake.