Apologies again for the delay. Photobucket is working again, so I can post the images.
This is the news report Franck posted.
Franck posted an image showing all those in the royal box. Below is another of the images which accompanied the report. (I am not sure if I ever posted this previously) Although the image is of very poor quality, the dark centre can be seen.
I think that Queen Mary was wearing what I call the wing tiara with the Ladies of India carved brooch in the centre (instead of the large sapphire).
Queen Mary wore the tiara with the Ladies of India brooch quite frequently to the theatre.
In the photos below, the brooch can be seen more clearly.