Around 5,000 officers were on duty to control the huge flag-waving crowds, alongside around 1,000 soldiers lining the route from Westminster Abbey to Queen Elizabeth’s London residence, Buckingham Palace.
Specialist teams with sniffer dogs had patrolled the procession route searching for explosives, while helicopters buzzed overhead as part of the operation to protect Prince William and his new wife Kate Middleton.
By 1000 GMT, a Metropolitan Police spokesman said there had been 18 arrests, including one on suspicion of sexual assault, three for being drunk and three for theft.
Spectators who waited hours for a glimpse of the royal couple in their open-top, horse-drawn carriage said the mood was jubilant, despite the crowds and heavy police presence.
“Considering the number of people here, it’s all very light hearted,” said Becton Davis, 42, who lives in London but is originally from North Carolina. “The atmosphere’s lovely.”
Police said they were aware of about 10 protesters in Soho Square, central London, from the “Right Royal Orgy Group” and they were monitoring them. There were also 70 demonstrators in Red Lion Square from the “Republican Tea Party” — another anti-monarchy group — and they too were being watched.
A handful of protesters gathered in Trafalgar Square, where crowds were watching the proceedings on a giant screen, and displayed a banner complaining about government cuts to public services and Britain’s military role overseas.
“The point I am making is for a silent minority,” said one of the protesters, who declined to give his name. “If people want to celebrate in the UK, do not do it at our expense.”
Earlier, three people — two men aged 45 and 68 and a woman of 60 — were detained in southeast London on suspicion of conspiracy to cause a public nuisance and breach of the peace. They were suspected of planning to behead royal effigies.
A fourth person, described by police as “a well-known anarchist” was arrested in Cambridge, northeast of London.
Police were prepared for a wide range of possible threats, from Irish republican militants to Islamist groups, anarchists and stalkers.
The London force was criticized for its handling of student protests last year when demonstrators attacked a car carrying Prince Charles and his wife Camilla Duchess of Cornwall.
The huge operation to keep the crowds safe and to ensure that London’s often unpredictable transport network runs well was seen as a test before the city hosts the Olympics next year.
“In many ways it is a good dry-run for the Olympics,” said London Mayor Boris Johnson. “It is a good opportunity to test our systems.”
