ISORI

〜たら最後(さいご)

JLPT N1:

once X happens, inevitably

Warns that once X happens, an uncontrollable and usually undesirable consequence will continue or become unavoidable.

How to form it

  • Put the verb in the たら conditional and add 最後(さいご): 始(はじ)めたら最後(さいご).
  • The result is difficult or impossible to stop, reverse or escape.
  • たが最後(さいご) is a more literary variant.

Examples

彼(かれ)は話(はな)し始(はじ)めたら最後(さいご)、なかなか止(と)まらない。

Once he starts talking, he simply will not stop.

この秘密(ひみつ)が外(そと)に漏(も)れたら最後(さいご)、計画(けいかく)は中止(ちゅうし)になる。

Once this secret leaks, the plan will inevitably be canceled.

Common mistakes

  • Using it for a reversible, neutral sequence.
  • Reading 最後(さいご) literally as the final event.

Same form, different meaning

  • 〜たらif / when

    Ordinary たら gives a condition or time; たら最後(さいご) warns that its consequence cannot be stopped.