London (CNN) -- British police chiefs on Tuesday warned protesters planning to disrupt the royal wedding that they will be dealt with "robustly and decisively."
Outlining plans for one of the biggest security operations ever held in the UK -- over 5,000 officers are involved -- police chiefs admitted however that they have no "specific intelligence," to suggest a terrorist threat.
Commander Christine Jones of the Metropolitan Police said: "In London we operate on a daily basis against the backdrop of a severe threat from international terrorism but we have no specific intelligence to suggest a threat to this event at this time."
Police said that Muslims Against Crusades, an Islamist group, had refused to agree to conditions on a protest march during the wedding day and had also failed to attend a meeting with police last week.
A counter demonstration is also planned by the English Defense League, an extreme right-wing group which has staged protests against radical Islam in recent months.
Some anarchist and anti-globalization groups have also threatened to protest in London during the day of the wedding.
"We have been working closely with officers investigating recent demonstrations... bail conditions have been imposed on over 60 arrested people who will not be allowed to enter London on the day of the wedding," said Commander Jones in a press conference.
Tens of thousands of people are expected to enter London for the big day and the Metropolitan Police asked the public to be their "eyes and ears," to help with the security situation.
Roy Ramm, former commander of special operations at the Metropolitan Police, said: "A million people will probably be on the streets and there are some who are going to try and disrupt. How close they can get to the wedding parade is the biggest fear, for the police it will be a balance of allowing people to get close but not being too intrusive while focusing on those behaving strangely in the crowd."
While terrorist groups, anarchists and other political extremists are the most obvious potential security threats to the royal wedding, the most potent danger comes from obsessive lone operators, say experts.
These 'fixated' individuals are such a threat that in a small office not far from Buckingham Palace in central London a team of psychiatrists, psychologists and police officers are busy trying to counter that threat.
The team is part of the Fixated Threat Assessment Center (FTAC), a unit established in 2006 with the responsibility of identifying and the power to indefinitely detain individuals who harass, stalk or threaten the royal family and others in public life.
A forensic psychiatrist, Dr. David James, is the clinical director of FTAC and has conducted research into attacks on the Royal household.
"The royal wedding has become the focus of attention for various fixated individuals who have responded by making threats to disrupt events -- some for deluded paranoid reasons and others because they believe themselves already to be married to Prince William. Such individuals generally meet the criteria for compulsory care under the Mental Health Act," says James.