Last year DD's classmate got her eagerly awaited telephone call from SAHS on the same day as the acceptance deadline. She must have been pretty near the top of the list, because 2 others never got that call and are still on the waiting list almost a year on
Apparently, if they have any spaces available after the deadline, they action the waiting list pretty quickly in strict order of ranking (exam & interview) making verbal offers first, then if accepted, then they follow up in writing.
I expect this is similar to all the other highly selective independent schools in North London & the surrounding areas - all competing for the same girls. Therefore if they have a few spaces still available, then they will all want to secure those highest up their waiting lists - so they action the list pretty quickly.
It is therefore crucial to have that phone glued to your side
at all times over the next few days
. (not sure what they would do if you are next on the list and you are not contactable at the time - you never really know if they will just move on to the next one on the list