"When you book a top-price seat for the evening performances on 18, 21 or 25 November you will pay £39.60 (usual price £66), and for the matinee performance on 15 November you will pay £31.20 (usual price £52).When booking for this special offer, choose Orchestra Stalls, Stalls Circle or Grand Tier and enter your preferred number of seats next to the 'email offer' concession."
Here is the link to the Royal Ballet ticket site in the email. I just checked the website. They may have assigned a certain number of seats to "email" offer, because I didn't see any available in Orchestra Stalls for the 18 November performance. (If available, they are displayed on a separate line with the special price.) To see availability after selecting a specific performance of "Polyphonia Triple Bill," click on the picture of the section on the left side of the screen.
I hope someone will see this, take advantage of the offer, and post about the performance(s). I'm jealous that I won't be able to see this program



