TfL have child Zip photocards for travel on their services from age 5. How many cards can you have? If held by the child that will last a few days before it is lost/forgotten. If held by parents what if both travel with the child separately - one takes to school, the other picks up. If you apply for duplicates (£10 a time) is the previous one cancelled, or are multiples allowed? There's no provision to say how many you want.