It's a long story, but...

Meaning

Prepares for a lengthy anecdote.

Examples

• John: Why are you so late?
• Alice: <b>It's a long story, but</b> I had a flat tire and then a traffic jam.
• John: Oh dear!
• Alice: Yes, <b>it's a long story, but</b> let's just say it wasn't a good day for driving.