According to ITV:
This year marks the 100th anniversary of both the Tomb, inside Westminster Abbey, and the Cenotaph in Whitehall.
The Queen laid a bouquet of orchids and myrtle flowers on the tomb which was based on her own wedding bouquet from 1947.
All Royal brides since the Queen’s mother…have placed their wedding bouquet on the grave of the Unknown Warrior in…remembrance.
The Unknown Warrior became an important symbol of mourning for bereaved families, as he represented all those who lost their lives in the First World War but whose place of death was not known, or whose bodies remained unidentified.
