Hi my dad is 63 and I decided to put his details in the NHS book vaccine website and it allowed me to proceed and pick a date and time and location for the booking. When I tried with my mum (60) it said she is not eligible to book through the service. However, my dad has refused to book saying he needs to wait for his letter and not skip the queue. As the website allows him to book, does that mean a letter is on its way to him?