The intruder who gatecrashed Prince William's 21st birthday party is an actor publicising his Edinburgh show, his father has said.
The man was handcuffed and driven away by police
Fred Barschak said his son, Aaron, was in his "comedy terrorist" character when he breached tight security at the Windsor bash.
A 36-year-old from London has been released on bail after being questioned by Metropolitan Police officers, and Home Secretary David Blunkett has ordered an immediate inquiry into the security operation.
The unarmed intruder managed to get inside Windsor Castle as 300 guests celebrated with the prince and other senior royals on Saturday night.
No one was injured during the incident at the African-themed party, but Scotland Yard said the matter was being treated seriously.
On Sunday evening, a Scotland Yard spokesman said: "The man has been bailed to return to a London police station on a date next month pending further
Earlier on Sunday, Prince Charles and the two younger princes played in a charity polo match in Gloucestershire.
Among the 700 spectators were friends of the princes who attended the party, but they refused to comment about what happened.
It is unclear how the intruder got into the castle.
Hours before his arrest, Mr Barschak had been moved on by police officers as he shouted to crowds outside the gates dressed as Osama Bin Laden.
But his father said he was only seeking publicity ahead of the Edinburgh Fringe Festival.
Aaron Barschak has previously confronted Ken Livingstone on a peace march, and Graham Norton at the London Comedy Festival.
Fred Barschak, 72, said: "He would not have been trying to harm anyone, not at all. He is actually not at all anti-royal."
The intruder reportedly stumbled onto the stage as Prince William made a speech thanking Prince Charles and the Queen for organising the party.
BBC correspondent Clarence Mitchell said departing guests described how the man grabbed the microphone before security guards and police pulled him away.
The intruder shouted out that he was Osama Bin Laden, and as he was driven away in handcuffs he was seen clutching a book about the al-Qaeda leader.
He was initially questioned at a Thames Valley police station before being transferred into the custody of Metropolitan Police officers on Sunday.
Our correspondent said that in these times of suicide bombings, the possible horror of such a security breach could not be contemplated.
Police and royal security advisors are reviewing the incident, with an independent senior officer placed in charge.
A Home Office spokeswoman said: "Depending on the outcome, [David Blunkett] may ask for a further inquiry."
A Scotland Yard spokesman said: "We consider any breach of security to be a serious matter and a thorough review into all the circumstances surrounding the incident is under way."
Prince William's party was for family and friends
A St James's Palace spokeswoman refused to comment on how the incident had affected the Royal Family and other party guests.
The party theme - Out of Africa - was inspired by the prince's time in Africa during his gap year before university.
All members of the senior Royal Family were present, except Prince Edward.
Others in attendance included Camilla Parker Bowles, Earl Spencer and his sisters, and William's friends from St Andrews University in Scotland.