Organiser Julia Stevenson read a poem sent by Lee Rigby's mother, Lyn Rigby:
The day is fading and the night is drawing near, the setting of the sun for a life we hold so dear.
The darkness is not forever, for again the day will come, and new light will surround us and engulf us all as one.
We'll manage through these bad times, we'll struggle through the storm. We'll tread amongst the roses, we'll pull the painful thorn. Yes, we know that we will miss you, but that's for us to bear,
For we know that you are safe now, and you don't have to care. Goodnight our son, brother, uncle, father and soulmate.
Goodnight my fellow soldier friend, goodnight our peaceful warrior. In your memory we'll defend.
London's mayor dismissed fears a permanent monument might become a magnet for extremists.
Lyn Rigby speaks exclusively to Good Morning Britain about her ongoing grief and described why she will never forgive her son's murderers.