A TOP secret new SAS base is under construction — at the Olympics.It means the elite troops can combat any terrorists at next year's London Games in an instant, The Sun can reveal.
A source said last night: "It reflects the gravity of the threat."
Chinook helicopters have been in action over the capital for months ferrying special gear to the new East London HQ.
Underground bunkers will house even more crack troops.
The SAS will have a key role in massive security at the Olympics — using "black ops" BOATS to swoop via the Thames if terrorists attack.
A secret new riverside base being built for the Who Dares Wins heroes in East London will be home to a fleet of the high-powered rigid inflatables.
It means elite units can speed there "in seconds" using the network of waterways around the Olympic site that make it an island — with no fears about being held up in London's notorious traffic.
The plan to enlist Old Father Thames as an ally was hatched as part of a ring of steel that will be thrown around the London Games next year.
A source said last night: "All scenarios are being anticipated. London will be protected like never before — and the message is clear.
"If anyone is fool enough to try to endanger the public at these Games they will be met with the swiftest retribution by the best-equipped troops of our most elite fighting units."
A fearsome arsenal of weapons will be housed at the new SAS HQ along with the boats. Firepower will include sub-machine guns, assault and sniper rifles, stun grenades — like those famously used in the Iranian Embassy siege — and teargas launchers.
The SAS will also have biochemical suits on standby in case of a "dirty bomb" attack.
Anti-terror chiefs believe the biggest threat is from al-Qaeda.
With the eyes of the world on the London Games — and Brits cheering on athletes such as Sheffield's heptathlon ace Jessica Ennis, 25 — bloodthirsty fanatics would glory in staging a Mumbai-style massacre.
To combat the threat, a network of underground bunkers housing even more Special Forces will have been constructed in time for the opening ceremony.
Helicopters will also be at the ready to fly in reinforcements. Our source said of the SAS's task at the Olympics: "They've been preparing for months. It's a huge mission and reflects the gravity of the threat."
The £486million Olympic stadium sits on former industrial land between the Old River Lea and the City Mill River. Other waterways including St Thomas' Creek mean it is surrounded. People injured in any attack could also be swiftly evacuated by river.
The source said: "Troops can deploy by air and water and be on site in moments. Then you've got force on the ground while the situation is monitored by the air.
"Major evacuation plans are still being revised in case of a terrorist attack. But the most important thing is having the access and ability to strike back at terrorists.
"That will be achieved and those plans are in place."
The Sun told in May how the SAS fired off live ammo at the Olympics Village — as they practised tackling a hostage crisis like the one at the 1972 Munich Games that saw 11 Israeli athletes and coaches massacred.
In July we revealed the Special Boat Service — sister force of the SAS — was in training to thwart suicide bombers off Weymouth in Dorset, where 60,000 sailing fans will flock to Olympic events.
Yachts there will also be guarded during the Games by Chinook helicopters operating out of RAF Odiham, Hants.
Last night the MoD refused to comment on the latest anti-terror plans.
By RICHARD WHITE and DAVID WILLETTS taken from http://www.thesun.co.uk/sol/homepage/news/3911459/Olympic-HQ-builtbr-in-secret-for-SAS.html