From Longman Dictionary of Contemporary Englishtake the biscuittake the biscuitBritish English informalSURPRISED to be the most surprising, annoying etc thing you have ever heard syn take the cake especially American EnglishI’ve heard some excuses, but this really takes the biscuit! →biscuit
Examples from the Corpus
take the biscuit• Now this just took the biscuit.• This really takes the biscuit!!• Clive Anderson O, while the mighty Sultans take the biscuit.