A laboratory hailed as the most high-tech in the history of the Olympics has been unveiled.
The lab is the centrepiece of the fight against doping at London 2012.
Organisers said the new Essex-based facility, estimated to be the size of seven tennis courts, will carry out more tests than at any prior Olympics.
The lab will operate 24 hours a day during the games, ensuring that every medallist and more than half of all competitors will be tested.
Pharmaceutical giant GlaxoSmithKline has donated and equipped the lab, which the company says is the major part of its £20m contribution to the games.
More than 1,000 people - mostly volunteers - will be involved in all aspects of collecting and processing samples.
The key work of analysing and determining if a sample is drug-positive or negative will be carried out by a team of more than 150 anti-doping scientists, flown in from all over the world.
They will be led by Prof David Cowan from King's College London.
He promised "super-fast and super-sensitive technologies to be able to detect the use of prohibited substances".
Speaking at the unveiling, UK Minister for Sport and the Olympics Hugh Robertson promised there would be no place to hide for cheats.
"We cannot absolutely guarantee that these will be a drug-free games," he said.
"But we can guarantee that we have got the very best system possible to try and catch anybody who even thinks of cheating."
Even though the laboratory is based near Harlow in Essex, the organisers are promising that all negative results will be turned round within 24 hours.
Positives will be returned in 48 hours, with the exception of the endurance boosting drug erythropoietin (EPO), which will take 72 hours.
Prof Cowan believes that athletes who use the courts to challenge the process of testing will be wasting their time.
"When people try to challenge, they won't be successful," he said. "We are going to be fast, sensitive and efficient, and we are going to be right."
This will be the first time that a pharmaceutical company has sponsored an Olympic anti-doping lab - but according to GlaxoSmithKline chief executive Sir Andrew Witty, there is no conflict of interest.
"Our involvement is the support and delivery of the facility; we have no role in the testing process," he said.
"We're not involved. You can be 1,000% reassured that there's no overlap, no conflict."
Not only is GlaxoSmithKline paying for the new lab, it has also entered into an agreement with the World Anti-Doping Agency (WADA) to share information on all their drugs, including products under development.
Sir Andrew now wants other firms to follow suit.
"If we could get that done on a broader basis, it would really close the net on people's potential to come up with molecules that WADA just weren't familiar with," he said.