The Bay, an ITV crime series starring Morven Christie, uses a foster care character in Series 2 (2019) as a courier for crimes.
Cassie is a 12 year old in foster care who delivers a gun to a hitman. She's done other deliveries before but not for anything so serious.
The character didn't need to have been in foster care. Already in Series 1 there was a police officer's 15-year-old acting as a courier for a drug dealer.