If you received a unique promo code by email, you can get 10 GBP off (valid from 25/3/19 at 12:01 AM CET to 14/04/19 11:59 PM).
At checkout on StubHub :

1. Tap 'Promo codes and gift cards' and the + sign
2. Enter [your code] and tap 'Add'
3. Tap the discount to apply it to your order and Save
4. Complete your purchase
Important: While supplies last. Not valid for events outside of the UK, parking passes, and gift cards. Offer redeemable once (UK only). Cannot be combined with other offers. No cash value, improper use of code prohibited. StubHub may modify or discontinue this offer at any time without notice. Void where prohibited.