Oh dear. Inability to say no or proving additional viability? How much of a legal minefield if these troops are to replace badged SIA? London 2012: Army reinforcements called in for the Olympics | Sport | guardian.co.uk The military is poised to provide up to 3,500 extra troops for security duty at the London Olympics, the Guardian can reveal. The last-ditch move has been forced on ministers only a fortnight before the Games because the security firm G4S has been unable to guarantee it will be able to supply the 10,000 guards it was contracted to deliver. The home secretary, Theresa May, has been pressing G4S to provide guarantees it can deliver on its commitments, but patience in Whitehall ran out last weekend and talks began over whether the Ministry of Defence could fill the gap. "The army will provide an insurance policy," said a Whitehall source. The armed forces are already providing up to 13,500 personnel for the Games - split between the venues and back-up for police. Under the contingency plans, this could reach 16,500 7,000 more than are being deployed in Afghanistan. The MoD has been seeking guarantees that any soldiers drafted in at the last moment will be properly compensated for cancelled leave. This latest move will raise fresh questions over the extent to which the Games will appear overly reliant on the armed forces last week it was confirmed that surface-to-air missiles would be located at six sites around the capital. The navy's biggest warship, HMS Ocean, will be stationed in the Thames and four Typhoon fighter jets will be on standby at RAF Northolt in Middlesex. Armed Puma helicopters will also be on standby. The issue of venue security has been the most contentious for organisers and the government in the runup to the Olympics. The total number of staff required to guard the Olympic venues more than doubled to 23,700 last December after the event's organiser, Locog, wildly underestimated the total required. Originally, Locog contracted G4S to provide just 2,000 security guards of the 10,000 it thought it would require. But in December, G4S agreed to supply 10,000 of the new total of 23,700 under a new contract reported to be worth £284m. 'Our people didn't sign up for Queen and country to check bags' Philip Hammond isn't everyone's cup of tea at the Ministry of Defence, but he's no pushover, and he has accounted for every penny in the over-stretched military budget. His calculations didn't include offering even more troops for the security of the Olympics, and being a stickler for detail, the defence secretary has been beavering around Whitehall in recent days making plain he has no intention of picking up the bill. That may be the least of the MoD's worries as it draws up yet more plans to cancel leave and deploy up to 3,000 extra troops, some of whom may have only recently returned from Afghanistan. None of which will do military morale much good, coming just a week after Hammond announced a raft of defence reforms that will see 20,000 posts lost from the army in the next three years. Anger within the armed forces at the manner in which the MoD has been called to the rescue has been replaced by weary resignation after a year in which the overall number of military personnel needed for Olympics duty has ballooned. The situation has been caused by a huge miscalculation by the Olympic organisers, Locog, followed by what appears to have been over-optimistic recruitment and training assessments by the security firm G4S. Locog first realised it had a major problem last summer, when its predictions for the number of staff needed at the Olympic venues began to unravel. It had thought it would need 10,000 people to undertake routine security checks, but when organisers started doing role-playing exercises at some of the new stadia, they began to appreciate this was a woeful underestimate. More than twice that number would be required. The Metropolitan police could not help because its staff were already accounted for. (Senior officers say they had been warning Locog for months it had got its sums wrong). And with the Olympic budget set, there was a reluctance to pay G4S to make up the shortfall. As ministers started to panic during the Cabinet Office briefings known as Cobra all eyes fell on the MoD. The military had already committed a number of ships, aircraft and ceremonial personnel to the Games, but it had not bargained for and was initially resistant to providing huge numbers of troops at the venues. "The military will do what they are told, but I don't think any of our people signed up for Queen and country to check bags," said one senior army officer. Though the problem was identified a year ago, the haggling over who would do what and when, and who would pay, didn't end until December last year, shortly after posters began to appear at the MoD's Whitehall headquarters advising staff to take out comprehensive holiday and travel insurance for the summer. Days before Christmas the government announced that up to 13,500 military personnel would be deployed at the Olympics, including 7,500 doing security checks at the busiest times during the Games. More than 2,000 reserves were called up in the spring to help make up the numbers. Even with that, Locog and the Home Office were relying on G4S to provide a total of 10,400 licensed security guards five times more than had originally been envisaged. The contract is reported to be worth £284m. Last autumn, G4S made it clear it could only recruit substantial numbers if it was given enough time. With time now running perilously short, it seems it is struggling to meet the commitment. Last weekend, only half the guards needed to guarantee fully staffed patrols of the entrances to venues and undertake other security duties were ready to start work. G4S admitted it had been having "some challenges on workforce scheduling", but insisted it could resolve them. Earlier this week it was reported that it still needed to train and accredit as many as 9,000 guards and was calling in retired police officers to fill vacant roles. On Wednesday, G4S declined to give a specific figure, saying the picture was constantly changing. A spokesman added that it remained confident it would meet its commitment by the start of the Games. In Whitehall, though, patience is running thin. With the Games only a fortnight away, the home secretary, Theresa May, has been co-ordinating talks about how best to provide cover. Inevitably, she turned to her cabinet colleague, the defence secretary. Hammond has been involved in many of the discussions, and though it would be inconceivable for the military to turn down such a request, he has made it clear it will cause avoidable inconvenience, which must be properly compensated. The MoD will not grumble in public. Earlier this year, General Sir Nick Parker, commander of land forces, said he was unconcerned that the military was required to help the Olympics at short notice. "I am entirely comfortable with the warning time. Short notice, rapid reaction, flexibility is what we do. From my perspective, 12 hours to grab your kit and go is short notice this is not. And let me reiterate that the feeling amongst military personnel about their involvement in the Olympics will be excitement, pride and a determination to do a good job." Parker did not know then how prophetic those words would be. With only days to go to the biggest sporting event ever held in the UK, the troops are on standby again.