Thanks for letting us know it worked. The discount can’t be retrospectively added, but it will change the cap that’s applied if you reach it, so the most you’d have paid for that day would be the discounted cap. Obviously not much consolation if you didn’t reach the cap, but it’ll definitely work from now on. Final point, whenever you renew the railcard you need to get the discount re-applied as it stops when the expiry date of your current card is reached.