When the young soldier boarded the shuttle bus, we knew we'd arrived at the Olympic site.
A polite man in green fatigues and a beret, he glanced only briefly over the reporters crammed into the top level of the double-decker bus ferrying us to the main venue.
With a nod, he wished us a good day and disappeared. Outside, meanwhile, his colleagues were using mirrors to check under the vehicles for explosives.
More soldiers stood watch behind gravel blast barriers, the kind used at military outposts in places like Afghanistan, and only rarely in places like civilized central London.
The military presence at the Olympic Park is hard to miss and is but one aspect of the super security, readiness concerns and political tensions that are dominating the run-up to this event.
At the main venues, workers are still scurrying to put the finishing touches on sites that will soon host visitors from around the world.
With the clock ticking down to Friday's opening ceremony, activity is increasing at the main Olympic Park with soldiers, security guards and reporters all trying to familiarize themselves with the sprawling collection of strange looking modernistic buildings.
Soldiers are now operating the X-ray scanners and metal detectors at the International Media Centre and men and women in fatigues are everywhere around the Games site.
Add to this the 5000-volt electrified fence (17.5 kilometres) that surrounds the Olympic Park, the ever-growing reach of the closed-circuit TV cameras that constantly watch over Britain's capital, and the plans to put as many as six surface-to-air missile batteries atop downtown buildings, and it is hard not to think of London right now as a city under siege.
The military has set up camp in an abandoned shopping centre in East London, near the Olympic park, installing beds and showers for some of the additional 3,500 troops — almost as many as Britain deployed in Afghanistan — who have been quickly called into service.
They are part of a 50,000-plus security force that includes police, the army and private contactors — the latter part of a multi-billion-dollar firm with mucho egg on its face.
Olympic organizers were forced to call on more troops only days ago when the security firm G4S admitted it could hire and train fewer than half the 10,000 security guards it had promised to patrol and protect the venues.
The head of the company, Nick Buckles, admitted the setback was, in his words, a "humiliating fiasco."
The British press, which loves nothing more than a good scandal, seized on the snafu and began sounding alarm bells about being vulnerable to a possible terrorist threat.
But with just four days to go before the opening ceremonies, Olympic organizers — who have spent more than $1.5 billion safeguarding the event — were promising athletes and fans were in no danger.
"This is not an issue that has remotely compromised security," said Sebastian Coe, the head of the London Olympic organizing committee in an interview with the BBC, referring to the G4S fiasco.
"We have got the numbers, courtesy of the military and our police services. We have got the numbers to make sure that this is a safe and secure games."
The concerns over security, though, are just one part of the opening night jitters Olympic organizers are experiencing as their big day draws closer.
The London Olympic Committee describes the Games as akin to staging nearly 50 world championship sporting events at the same time.
Organizers are trying to accommodate nearly 15,000 athletes and 21,000 journalists while coordinating an army of 6,000 staff and 70,000 volunteers.
On top of this, the British government has put a special team of diplomats and protocol experts in place in case heads of state, such as Russia's Vladimir Putin, decide to show up at the last minute; or in the event there is a need for secret, high-level negotiations among some of those in attendance.
All in, London 2012 is a logistical nightmare. And it almost goes without saying that many things can and will go wrong.
There have already been grumblings here about traffic tie-ups and the general disruptions that go hand in hand with holding an event of this scale.
London cabbies held an impromptu one-day park-in last week and there are concerns that passport officials and train crews may go on strike during the Games.
London's flamboyant mayor, Boris Johnson, though, is having none of the gloom and doom. A shameless promoter of both the Games and his beloved city, Johnson has lashed out at the doubters and urged all of Britain to feel a swell of national pride at holding such a prestigious event.
"Oh come off it, everybody. Enough whimpering," Johnson wrote in The Sun tabloid newspaper recently.
"We are about to stage the greatest show on Earth in the greatest city on Earth, and if you believe much of the media we are all in the grip of paralyzing stage fright."
On Friday, as thousands gathered along the banks of the River Thames to watch the Olympic flame arrive in London aboard a Royal Navy helicopter, many seemed to share the mayor's view.
"It's kind of very British thing. We always seem to look at the downside rather than the upside", said Jackie Barlow of South London.
Barlow has tickets to Olympic field hockey and soccer matches and fully expects the Games to be a great success.
"There will be disruptions, there's no doubt about it," she says. "But there are disruptions on a normal day. So, people will just have to be patient. It's going to be fun."
"The British love to moan about things. It's the way we are, "said Sarah Jane Breen. "But we'll just get on with it. Everyone's going to have a great time."
Over the weekend, that sentiment seemed to be taking hold. Thousands lined London's streets to watch and cheer the Olympic torch on its tour through the city. The sun came out and, after weeks of dreary weather, Londoners were able to bask in what felt like their first summer day of the year.
Organizers of the Olympics can only hope it's all a good omen and that this huge international undertaking unfolds without incident. Ready or not, the London Games are about to begin.