TMZ has learned what triggered the drama last Thursday night that ended with Britney being strapped to a stretcher and carted off in an ambulance.
Unimpeachable sources tell TMZ Brit pitched a fit that she had to attend a deposition in the custody case earlier in the day and she wanted "make-up" time with the kids that evening. Britney had visitation rights with the kids that day. She was supposed to surrender them to K-Daddy at 7:00 PM, but wanted two extra hours. K-Fed and his lawyer, Mark Vincent Kaplan, wouldn't allow it, so she locked herself in the house -- thus the stand-off.
Here are the probs with Brit's theory. First, the reason her depo was set for last Thursday was because she failed to show the day before. Second, Thursday's depo was supposed to begin at 9:45 AM and go until 11:45 AM. She didn't show until 11:32, so the depo lasted less than 15 minutes. We've learned she only had visitation rights that day between noon and 7 PM. The depo ended at 11:45 and her house was only 15 minutes away. So she really didn't lose any time with the kids.
Bottom line -- Brit was legally off base.