From Wikipedia:

The announcement tonight that the Queen will not take part in this coming week's Maundy Thursday service is unprecedented. It has been a fixture in her religious calendar throughout her 70-year reign. Her place will be taken by Prince Charles.

While people assume that she is following in the footsteps of other royal monarchs, none of them was ever as assiduous as she has been in maintaining the tradition. It is a ritual that expresses her belief in what being a Christian monarch is about.

Medieval monarchs first practised the Maundy service ritual by washing the feet of the poor and giving alms to them. The first king recorded as doing so was John, who gave clothing, forks, food and other items to the poor in Yorkshire. Then in 1213, at a ceremony in Rochester, he gave 13 pence to 13 men, a number that was a reminder of Jesus and his 12 apostles.

Other monarchs followed, with Henry IV beginning the tradition that the number of pence given should reflect the monarch's age.

Some monarchs took the ceremony particularly seriously. Queen Mary I washed the feet of 41 women in 1556, the year of her 41st birthday, and also gave them 41 pence each plus other gifts of bread, fish, and clothes, including her own gown.

Later, court officials would wash the feet of the poor first before the monarch had to endure doing it. Charles II, after the Restoration, attended even during the plague years of 1661 and 1663.

By the 20th century, members of the royal family would attend, particularly Princess Helena, Queen Victoria's third daughter, and her own daughter, Princess Marie Louise.

The current Queen began the habit of taking the service around the country to different cathedrals. The service, though, always follows a similar pattern, with two New Testament readings.

There are two gifts: a white leather bag containing special Maundy coins and a red leather one containing other money.

A man and a woman are chosen for each year of the Queen's age, and the money also represents the years she has lived. The recipients are usually people being recognised for their service to the community.

Six silver dishes are used to hold the gifts; one, the traditional Maundy Dish, forms part of the regalia used at coronations and is held at the Tower of London when not in use. All six dishes date from the reign of Charles II.

For the Queen, at 95, and with mobility issues, the Maundy service would certainly be taxing, standing for a considerable time as she distributes the gifts.

To read the complete article, see:
The Queen withdraws from the Maundy service, a ritual that became a pilgrimage(https://religionmediacentre.org.uk/news/the-queen-withdraws-from-the-maundy-thursday-service-a-ritual-which-became-a-pilgrimage/)

To read an earlier E-Sylum article, see:
QUEEN ELIZABETH II DISTRIBUTES MAUNDY MONEY(https://www.coinbooks.org/v22/esylum_v22n16a21.html)