Castle Howard Proms for Two - Key InfoVoucher Validation Your voucher is valid until 01 Jul 20 You must validate book and use your voucher within the voucher expiry date.Duration: The concert last 2 hours.Group Size: This experience is for two people there will be other people there on the day.Weather Dependent: NoThere is no minimum age under 18s must be accompanied by an adult.Requirements: Please note no dogs are allowed.Availability: This concert takes place once a year subject to availability.