The president was expected to sign the official condolence book and attend a reception Sunday at Buckingham Palace hosted by King Charles III before attending the queen’s funeral at Westminster Abbey on Monday.

Biden is among many world leaders traveling to the United Kingdom to honor Queen Elizabeth’s long reign. Biden and first lady Jill Biden were greeted at the airport by U.K. Ambassador Jane Hartley, Lord Lieutenant of Essex Jennifer Tolhurst and others.

After the queen’s death, Biden issued a proclamation directing that all American flags be flown at half staff “as a mark of respect for the memory of Queen Elizabeth II” until sunset on the day of her interment. Before coming to London, he spoke with the king to offer his condolences and went to the British Embassy as well.