Truss, who was named prime minister by Elizabeth on Tuesday in her final public act, was one of several senior lawmakers who took a new oath of allegiance to the new king at a special session of parliament earlier in the day of Saturday following the death of the queen.
She was also present, alongside six former prime ministers, high-ranking bishops and several politicians, when Charles, 73, was officially proclaimed Britain’s new king in a colorful ceremony, charged of pageantry and tradition.
She then met Charles and other top ministers at Buckingham Palace.
“As for the Prime Minister’s participation, she will join the King as he leads national mourning across the UK, attending retreat services in Scotland on Monday afternoon, Northern Ireland on Tuesday and the Wales on Friday,” the spokesman told reporters.