From Paul Harris and Robin McKie in Britain's The Guardian:
Britain will get its first chance to see Barack Obama this week when a White House cavalcade - complete with armoured limousines, helicopters, 200 US secret service staff and a six-doctor medical team - sweeps into the UK.
Obama will fly into London for his first visit to the UK as president of the United States on Tuesday to take part in the G20 summit in the capital's Docklands area. He will not be travelling light.
More than 500 officials and staff will accompany the president on his tour this week - along with a mass of high-tech security equipment, including the $300,000 presidential limousine, known as The Beast. Fitted with night-vision camera, reinforced steel plating, tear- gas cannon and oxygen tanks, the vehicle is the ultimate in heavy armoured transport.
In addition, a team from the White House kitchen will travel with the president to prepare his food. . . .
US security teams have already carried out three visits to prepare for Obama's first official visit to Britain. The first was a "site survey", the second a "pre-advance visit" which was carried out to pick sites that the president would visit. Finally there was the "advance trip", which took place last week. Its purpose was to set up equipment, sweep venues for electronic bugs, test food for poison and measure air quality for bacteria.
Obama will start his first presidential visit to Europe when he steps down from the US presidential jet, Air Force One, at Stansted airport on Tuesday. The Boeing 747-200B is fitted with its own gym, electronic defence units and shielding to protect its complex communication devices from radiation from nuclear blasts. . . .
Obama will then be flown to central London in a VH-3D helicopter known as Marine One. Again, high-tech security will dominate his journey. Marine One is fitted with flares that can be fired to confuse heat-seeking missiles and always flies in groups containing several identical decoy helicopters. . . .
At the same time, Obama will be constantly minded by his personal aide Reggie Love, who dials his BlackBerry, fetches his jacket and tie and supplies him with snacks. First Lady Michelle Obama will also have a coterie of assistants, including a secretary, a press officer and several bodyguards.
It is a striking presence and shows that, for the next few days, London, not Washington, will be the beating heart of American foreign policy. At the end of the week Obama and his massive retinue will head off for meetings in France, Germany and the Czech Republic, although not before he has indulged in an unprecedented whirlwind of diplomatic activity - he and his advisers will not just be involved in complex summit negotiations, but will also be camped out in London conducting a series of individual high-level mini-summits with the most powerful leaders in the world. . . .
The president's entourage will also include representatives of the White House Military Office, the White House Transportation Agency, the White House Medical Unit, the Marine Corps Helicopter Squadron, the State Department Presidential Travel Support Service, the US Information Agency, the Immigration and Naturalisation Service and the Customs Service.
In addition, there will be staff from the White House kitchen ready to turn out a quick burger should the president suddenly feel peckish.
Michelle Obama will have eight of her own staff, including a secretary, a press officer and bodyguards. And Obama's personal aide . . . will be at hand to provide pens, Nicorette gum, throat lozenges, tea or even aspirins.
With its armour-plated body and doors, a raised roof, and reinforced steel and aluminium, The Beast will be Obama's official car. It boasts a titanium and ceramic superstructure and a sealed interior forming a "panic room" capable of shielding him from even a chemical weapons attack. Equipped with a night-vision camera and an armoured petrol tank filled with foam to prevent explosion should it suffer a direct hit, it also has pump-action shotguns, tear-gas cannon, oxygen tanks and bottles of the president's blood. Its tyres allow it to keep driving even if they have been punctured.