The procession is now getting under way as the royals make their way to the front of the cathedral – you can watch by clicking the play button at the top of this page.
Prince Charles is representing his mother during the service after the 96-year-old monarch pulled out of the high-profile occasion due to mobility issues.
The Duke and Duchess of Cambridge are being received by the Bishop of London and the Archbishop of York.
There is a cheerful atmosphere in the cathedral despite the absence of the Queen.
There appears to be lots of friendly chats going on, says BBC commentator David Dimbleby.
Prince Harry and Meghan, Duchess of Sussex have arrived at St Paul’s, getting a warm reception from the crowd.
It is the first big royal event they will have attended since stepping down from royal duties in 2020.
The royals arrive in a kind of reverse order of seniority.
It would have been the Queen who was the final arrival, but in her absence it will be Prince Charles, once again standing in for her.