How do I redeem a 2 for 1 Voucher? Please note: All guests, including those with promotional vouchers, must pre-book online in advance. For further information regarding Promotional Voucher redemption, please visit here. Related articles Can I use a 2 for 1 voucher at The London Eye? How can I redeem my National Rail Days Out 2 for 1 Voucher? How do I redeem my Kellogg's voucher to purchase an online ticket? Can I use my 2 for 1 online against the online price? Can I buy tickets on the day when I arrive?