Prince Charles and Prince William refused to meet with President Trump during his visit to the United Kingdom, according to London newspaper The Sunday Times.

A source familiar with the planning for the president and first lady Melania Trump’s meeting with Queen Elizabeth II told the Times that Charles and William made it clear that they did not want to participate.

“This business of Prince Charles and Prince William not being there for the Trump visit was a snub,” the source told the paper. “They simply refused to attend. It’s a very, very unusual thing for the queen to be there on her own. Usually she is accompanied by somebody. Prince Charles has been substituting for Philip a lot recently.”{mosads}

Prince Philip, who, at 97, has officially retired from royal duties, “goes to what he wants to go to,” the source said, adding that “if he had wanted to be there he could have been.”

The Trumps met with the queen on Friday for tea at Windsor Castle, sparking social media backlash among the British public after video showed the president walking in front of the queen. The move was seen as a sign of disrespect, though it did not technically break royal protocol.

Charles reportedly attended a board meeting for his company and an event with Gloucestershire police, while William participated in a charity polo match and Prince Harry attended other private engagements, according to the Times.

Trump’s visit was not a state visit, and other sources at Buckingham Palace and Downing Street told the Times that the plan had always been for Trump to meet solely with the queen, and denied the report that the refusal to meet with Trump was an intentional rebuke.

Former presidents have met with other members of the royal family in the past, and it is well-known that former President Obama and former first lady Michelle Obama are close with William and Harry and their families.

Neither the Trumps nor the Obamas were invited to Harry’s wedding to American actress Meghan Markle earlier this year, as the couple did not invite any political leaders.

Trump’s visit was marked by thousands of protesters greeting him in London and at his Turnberry golf course in Scotland. In an interview he gave to the tabloid The Sun, he also harshly criticized Prime Minister Theresa May.