séance tenante bedeutet auf Englisch

on the spot▼◼◼◼(at the very moment)
preposition
[UK: ɒn ðə spɒt] [US: ɑːn ðə ˈspɑːt]

right away▼◼◼◼(very soon; immediately)
adverb
[UK: raɪt ə.ˈweɪ] [US: ˈraɪt ə.ˈweɪ]

forthwith▼◼◼◼(without delay, see also: immediately; right away)
adverb
[UK: ˌfɔːθ.ˈwɪθ] [US: ˌfɔːr.ˈθwɪθ]

at once▼◼◼◻(immediately)
adverb
[UK: ət wʌns] [US: ət ˈwəns]