Britain has battened down the security hatches while a grandmother scaled the gates of Buckingham Palace to protest as the country braces for the US president to arrive. George Bush's guardians, fearing an al-Qaida attack, have insisted on top-level security, ruling out traditional events such as a horse-drawn carriage ride with the Queen through the city. The killing of 25 people in weekend bombings of two synagogues in Istanbul raised tension still further, with the capital on high security alert only too aware that a strike could come anywhere and at any time. But with all police leave cancelled in London and a record 14,000 officers on duty over the three-day state visit starting on Tuesday in anticipation of large-scale protests over the Iraq war, a newspaper poll gave Bush some cause to smile. **Lone Demonstrator*** An ICM poll in the Guardian said that in contrast to most theories, 43% of British voters welcomed the visit, while 36% opposed it. But that didn't deter veteran Quaker anti-nuclear protester Lindis Percy, who scaled the six metre high iron gates in front of the palace where Bush will stay for three nights after he arrives late on Tuesday. After unfurling an upside down US flag with the inscription "Elizabeth Windsor and Co. He's not welcome", Percy clung on for just over two hours before climbing down and being whisked away in a police van. The UK Prime Minister Tony Blair has responded to those critical of the timing of the visit by insisting Britain was right to join the US in "defeating terrorism". He said recent terror attacks in Turkey and Saudi Arabia, and in Iraq on the UN and Red Cross, illustrated the dangers faced by the world. "This is the right moment for us to stand firm with the United States in defeating terrorism wherever it is and delivering us safely from what I genuinely believe to be the security threat of the 21st Century," Mr Blair told a CBI conference in Birmingham on Monday. **Mass Protests*** Organisers of a major protest march through London planned for Thursday rejoiced when police finally granted permission for them to parade past key government buildings where Bush will be holding meetings. An estimated 100,000 people are to participate in the demonstration. At the climax of the march in Trafalgar Square, protesters will topple a giant effigy of Bush in a symbolic repeat of the destruction by US troops in April of a statue of Iraqi President Saddam Hussein. "This does not mean that we support Saddam. He was a nightmare. But what Bush has done has not helped ordinary Iraqis at all. There is chaos there. Children are dying every day," Mell Harrison, 32, of the Theatre of War activist group said. Police snipers will line the president's route on rooftops and all the capital's rapid response armed units are on full alert. Mr Bush will also be protected by hundreds of armed guards from the US. They will not be granted diplomatic immunity, and will be subject to the British legal system if they shoot anybody, the Home Office has promised.