(Exclusive) Prince Harry’s Emotional Tribute to Late Uncle Leaves Guests ‘Astounded’ and Him ‘Pleased,’ Source Says

“He was on remarkably good form — and you could tell he was very pleased to see everybody,” a source tells PEOPLE of the Duke of Sussex’s appearance at a memorial service for his uncle.

At the Aug. 29 service at St. Mary’s Church in Snettisham, Norfolk, the estranged brothers sat apart, each with different groups of their maternal cousins.

“Most people were astounded that Harry came,” one of the reported 300 attendees tells PEOPLE. “He was on remarkably good form — and you could tell he was very pleased to see everybody.

And he was very pleased that he had come over.” Many guests, including members of the extended Spencer family and friends, gathered around Harry — who turns 40 on Sept. 15 — to speak with him at the service, according to the source.