The Queen has pulled out of the annual Maundy Thursday church service for the first time since 1970.
Her Majesty will instead be represented by the Prince of Wales, Buckingham Palace announced.
The service is to take place on 14 April at St George's Chapel, Windsor Castle.
It will be the first time that the Queen has been represented at the service by Prince Charles.
He will be accompanied at the event by the Duchess of Cornwall.
The service takes place each year on Maundy Thursday - also known as Holy Thursday in some countries.
The holy day falls on the Thursday before Easter Sunday and commemorates Jesus washing the feet of his disciples at the Last Supper.
At the annual church service, silver coins called 'Maundy money' are traditionally distributed to local pensioners.
The Queen's withdrawal is reported to have been decided a week in advance in order to avoid disruption to the service.
It comes at a time when the Queen has been experiencing mobility problems.
Many recent engagements have been attended by the Queen virtually. At the Service of Thanksgiving for the Duke of Edinburgh last month, she used a walking stick.
A palace source told The Telegraph: "Mobility issues which emerge make it difficult for the Queen to predict in advance whether she can attend a particular event.
"If an event requires advance notice for the printing of orders of service and other material, such as Royal Maundy, that makes it much harder.
"She felt it would be best to make it clear at this stage that she would not be attending, in order not to overshadow the service by pulling out closer to the time."
