A man who sparked a royal security alert by paragliding into the grounds of Buckingham Palace has been released on police bail, Scotland Yard said last night.

The 36-year-old was bailed to return to a central London police station on an undisclosed date in the new year.

He was arrested for endangering the safety of aircraft under article 63 of the Air Navigation Order, which relates to traffic in a controlled area, a police spokesman said.

The man, struggling Australian author Brett De La Mare, was monitored by a police helicopter, which followed his progress across central London.

The escapade was witnessed by Chris Sims, city editor of The Herald, who said: ''It was quite extraordinary. I could see this motorised paraglider and thought . . . it shouldn't be here . . . it then turned towards the Mall and Buckingham Palace.''

With London at its highest level of terrorist alert for many years following intelligence that the Real IRA plans a so-called spectacular, Scotland Yard responded swiftly.

After landing his powered paraglider in the palace forecourt - scene of the changing of the guard ceremony - he was taken to a central London police station and interviewed by detectives from the Specialist Crime Operational Command Unit.

A palace spokesman said no members of the royal family were in the building. Senior members are currently at Sandringham, the Queen's Norfolk estate, for the Christmas and New Year period.

Following his release last night, Mr De La Mare said: ''I decided to breach security at the palace. I thought about getting shot, but the London police are famous for their restraint and their bravery.

''I am not a terrorist, and it is obvious I am not a terrorist.

''The chasing helicopter affected the canopy of my craft, but the pilot backed off when he saw what was happening.

''I was starting to get frostbite and it was really cold up there.''

Mr De La Mare said the chasing helicopter did not give him any great concern as he had been pursued in mid-air before. He had also flown a paraglider around the Empire State Building in New York, he said.

He said he made the flights because of his frustration at not having published a book that he had written. He was prepared to ''do what it takes to get noticed''.

Mr De La Mare said he would be on police bail until January 5, when he will be told of his fate.

He said he had six months' flying experience and claimed family and friends were behind his publicity-seeking exploits.

''They wouldn't be human if they didn't worry,'' he said. ''I had been planning to do this for some time. I studied the geography and the weather conditions.''

Mr De La Mare said he realised he could face jail for his exploits, but claimed if he secured a book deal it would be worth it.

Monica Kelly, a 22-year-old public relations executive from Brisbane, Australia, and flatmate of the flyer, said yesterday's stunt was a bid to get publicity for his manuscript Canine Dawn, which is set in the outback.

On his website, www.brettdelamare.com, which was promoted on the purple and white paraglider, the author had left an open letter to ''The Press, The People and Publishers''.

In it he says: ''I've written a book called Canine Dawn and I'm out to get published.

''Brother let me tell you so far it's been hell. But until it is (published) I'm prepared to do whatever craziness it takes.''

On the site he says he was arrested after his first attempt at self-promotion in New York two months ago, when he flew round the Empire State Building and the World Trade Centre.

A history of royal security breaches

l 1974: Gunman Ian Ball tried to abduct the Princess Royal as she and Capt Mark Phillips were being driven along the Mall.

l 1981: Marcus Sarjeant, 17, fired six blank shots at the Queen during a ceremony.

l 1982: Michael Fagan broke into Buckingham Palace and got into the Queen's bedroom. She awoke to find him sitting on her bed.

l 1993: A group of women anti-nuclear protesters used ladders to climb the walls at Buckingham Palace.

l 1994: A burglar gained access to the private apartments of the Prince of Wales at St James's Palace and stole royal heirlooms.

l 1994: Naked American paraglider Jim Miller landed on the roof of Buckingham Palace.

l 1995: John Gillard, 21, rammed the gates of Buckingham Palace with his car.

l 1997: Absconded mental patient Alastair Coe gained access to the palace grounds.