The King Edward's Crown has been secretly removed from the Tower of London to an undisclosed location for resizing.
The King Edward's Crown has been used for Coronations since the 11th Century and rebuilt in its current shape in 1661 (after vandalism by Oliver Cromwell). It can be seen in the Bayeux Tapestry.
It will return after the Coronation.
Don't let the absence affect your visit to the Tower of London - there is lots more to see in the Crown Jewels display.