More than 3,000 people including hundreds of Americans gathered outside Buckingham Palace yesterday to hear the Star Spangled Banner performed in an unprecedented alteration to the changing of the guard ceremony.

The Queen ordered the change to the daily ceremonial parade to show solidarity with the United States in the wake of Tuesday's terrorist strikes. Prince Andrew, representing his mother, was joined by the US ambassador to Britain, William Farish, for the 45-minute ceremony.

As the band of the Coldstream Guards began the US national anthem hundreds in the crowd sang along while others wept, before observing a two-minute silence.

Later the Queen returned to London from Balmoral, where she met Mr Farrish.

For many among the crowd it was an opportunity to pay their respects to the dead. "I want to be closer to home right now and this is the closest we can get," said Laura Esposito, 34, of Boston, who wore a jacket with the Stars and Stripes pattern.

At the US embassy in Grosvenor Square queues formed as a book of condolence was opened. Prince Charles was first to sign the book. The prince will today join the Queen and Duke of Edinburgh at a service of remembrance at St Paul's Cathedral. Tony Blair will also attend the service.