Prince Harry is returning to the UK next month for the first time since his rushed visit to see the King after his cancer diagnosis.
The Duke of Sussex will attend a ceremony on 8 May marking the 10th anniversary of the Invictus Games.
Thanksgiving at St Paul’s Cathedral is the first big event he has attended in the UK in a while.
It is unclear whether other royals will attend the service, or whether the Duchess of Sussex or the couple’s children are in the UK.
Harry took a short trip to the UK in February and spent about 45 minutes with his father, who had just started cancer treatment.
The Duke will give a reading at the event, which marks 10 years since the first Invictus Games in London in 2014.
The Games were established as a sporting event for injured or ill military personnel and veterans.
Actor Damian Lewis reads the Invictus poem during the service.
Representatives from all countries participating in the Invictus Games will also be in attendance, including members of the wounded, disabled, military and veteran communities.