The Archbishop of Canterbury said Monday he would miss a national service of thanksgiving for Queen Elizabeth II's Platinum Jubilee after testing positive for COVID.
Justin Welby, who leads the worldwide Anglican communion, said he was "deeply saddened" at missing Friday's service in St Paul's Cathedral, central London.
He was diagnosed with mild pneumonia on Thursday and developed coronavirus symptoms over the weekend, and has cancelled all engagements this week.
"However, I will be praying for the queen and giving thanks for her extraordinary 70 years of service to us all," the archbishop said.
"I will also be praying for our nation at this time of celebration and thanksgiving. May the queen's example bring us together in unity and care for one another."
The Church of England's second-highest ranking cleric, Archbishop of York Stephen Cottrell, will deliver the sermon instead.
Buckingham Palace has yet to confirm if the 96-year-old monarch will attend the Anglican service herself.
She has restricted her public engagements in recent months after complaining of mobility problems. She contracted COVID-19 in February.
Two figures set to attend on Friday are Prince Harry and his wife Meghan, according to their biographer Omid Scobie.
The Duke and Duchess of Sussex stepped down from royal duties and moved to North America early in 2021. They have visited the UK together only once, after a series of disputes with the royal family.