What time would you like to depart and arrive? I would recommend TR4119 which leaves London Liverpool Street at 21:39 and arrives in Cambridge at 23:07.
I am coming to Cambridge on Wednesday and need to take a train. I would be departing from london liverpool street. train needs to go to cambridge and should leave after 21:15 Can you book it for me?
{"__type": "Inform", "entity": {"__type": "Train", "arrive by": "23:07", "departure": "London Liverpool Street", "destination": "Cambridge", "leave at": "21:39", "trainid": "TR4119"}}
{"__type": "Request", "service": "train", "values": ["book people"]}
Of course, do you just need one ticket or will there be other passengers?