London Olympics chief organizer Sebastian Coe is promising safety and security at the Summer Games. An extra 3,500 troops have been drafted into service after international security firm G4S admitted a shortage of staff, and a further 1,200 troops are on standby. With less than a week to go before the opening ceremony, UK correspondent Richard Bestic has been looking at the challenges facing London 2012 and the measures put in place to counter them.

As the Olympic teams arrive in London for the Games in just 10 days, London is facing up to the biggest peacetime security operation in the UK capital’s history. Olympics Venues across the city are in a state of lockdown … subject to extensive and regular security sweeps.

Sniffer dogs used to check for explosives in what is a one-and-a-half billion-dollar security operation.

Planning based on a threat level of ‘severe’ – meaning an attack is ‘highly likely’, although that is one step higher than the current level across the UK.

The security operation is backed by a vast array of military and police assets.

Ground to air missiles in place around London.

Helicopters with snipers will patrol the air … along with Typhoon fighter jets.

Intense police training has focused on direct and close contact with suspected terrorists.

While one drill simulated an incident on the London underground in an echo of suicide bombings that killed 52 commuters in 2007 – a day after London won the 2012 Olympics bid.

The cost is high, but according to international security analyst Sajjan Gohel, the challenge is also high.

Gohel said, "You have terrorists associated with large-scale cells connected to al-Qaida; there are lone-wolf terrorists; dissident groups connected to or evolved from the IRA (Irish Republican Army); far-right elements - all of these groups have their own agendas, their own issues, and their own way of trying to exploit a situation for propaganda purposes. So the challenges are there.”

Reporter: "It’s against that intense backdrop Greg Buckles the boss of the private security firm G4S was grilled by furious Members of the British Parliament. They were furious. 3,500 British troops by Mr Buckles’ company"

Q: "Why are you still in your post?"

Chief Executive of G4S Nick Buckles said, "It’s not about me, it’s about making sure we deliver the contract. Secondly, I feel I’m the right person at the moment to make sure that happens and make sure that our company comes out of this with its reputation intact. "

With the latest additions, some 17000 military personal will be available during the Olympics.

But the government here is emphasizing that Olympic security will be led by the police with the military in support, not the other way round.

This is where the entire security operation will be coordinated during the Games - the special operations room of the National Olympic Coordination Centre.

Olympics Security Co-ordinator Chris Allison said, "There are determined people out there, but a variety of measures that we put in place ensure that thankfully they don’t get through. That’s work done by the security services, work done by the counter-terrorism command, the national counter-terrorism network, and the protective security measures that we put in place. "

There’s one thing going for London 2012 – when it comes to security, London is internationally recognized as possessing the highest levels of experience. If it can be made safe, this is the place.