I've just been checking out the RHS website ready for tomorrow's online Question and Answer session and it looks like you can set up questions ahead of tomorrow morning's 9.30-12.30 live discussion. There's a couple on there already and it means there's an opportunity to take part even if things like work prevent you from doing so tomorrow.
As I mentioned in my post last week, you need to be registered on the My Garden section of the RHS website in order to take part. Once you've done this, go to the Forum section and click on the RHS Directors Online Forum discussion thread. If you've already registered or just want read-only access, then this link will take you there. You'll see I've tested it out already by taking the Write a New Post option and asking how long the discussion will be available for viewing afterwards.
Thanks to those of you who commented last week - I've added your questions to my extensive list ready for tomorrow.