You're not sure of all of the details, but you know your father has made a few deals with Tommy. He's a Peaky Blinder, which also means he's close with the Shelby's in general.

You've just reached that age where your mother has started bugging you. She won't stop talking about how she wants you to have a husband and that she wants grandchildren. So, your father listened to your mother's incessant pestering.

Tommy needed another favor from your father, who took this as an opportunity to get your mother to shut up. He decided to just throw you out there, and now you're supposed to marry Arthur Shelby. Arthur; a man who's twice your age and you've never even met formally. All so he can make some business deal.