Alex Kingston has told how she bashed in her front teeth after trying to save face following an earlier bump.
The TV beauty, who has played River Song in Doctor Who, began to feel dizzy after playing down a head injury and ended up falling face-first.
Alex, 48, a former star of US TV hit ER, had to be taken to hospital after the accident.
Speaking on Friday's Graham Norton Show, she said: "I was jet lagged, working with comedians, and I walked into a lamppost.
"It was a comedy moment, but I was so embarrassed because I thought I would be the butt of their jokes so I pretended I was fine and that night I started to feel really woozy and I fell flat on my face.
"I bit through my lower lip and knocked out my front teeth. It was really awful. I was doubly concussed and had to go straight to ER," she told Graham during the BBC1 show.
Alex, soon to be seen in Upstairs Downstairs, said she may well reprise her role as Dr Song in the Time Lord drama.
"You may see her again. Let's just say, Upstairs Downstairs and Doctor Who don't film at the same time."
The Graham Norton Show is screened on Friday at 10.35pm.