There's a train on that route every day departing at 18:01 that ought to work for you. Do you know what day you'll be travelling? Where will your departure site be?
I'm looking for a train that is going to birmingham new street and leaves after 17:15. I will be traveling on Friday. I will be leaving from Cambridge. I will need 4 seats.
{"__type": "Request", "service": "train", "values": ["departure"]}
{"__type": "NotifySuccess", "service": "train", "entity": {"__type": "Train", "book people": "4", "ref": "HI8OJSIM"}}
Great I booked you 4 seats on that train and your reference number is HI8OJSIM .