I bought tickets in the Trainline app and one of the trains in my journey was severely delayed. I was entitled for a refund for the full journey. Trainline requires a physical copy of all tickets in your journey for the refund. If you are not able to provide the physical copy it will not be refunded. I had to use the ticket of one of my legs in St Pancras Intl to get out, for crossing to Kings Cross. The ticket was not returned in the gate. That part of our journey was not refunded, even there was an evidence that I bought the ticket in the Trainline. Once you start the refund process, the tickets are blocked and cannot be printed out again in the machines. Keep this in mind when you buy tickets in the Trainline app or website, you need to provide a physical copy of your ticket for a refund.