The Big Question: How prevalent is the use of drugs in sport, and can it be defeated?

Why are we asking this question now?

In the space of the last week, the presence of doping abuse at the highest levels has been highlighted by positive tests for two leading performers. Floyd Landis's recent victory in the Tour de France cycling race may now be expunged from the records if the test are confirmed after the presence of illegally high levels of testosterone were detected in a urine sample. On Saturday night, Justin Gatlin, the US world and Olympic 100 metres champion, announced that he had tested positive for illegal testosterone levels in a sample taken on 22 April. Having registered a previous doping infraction, the 24-year-old, who has been a highly vocal defender of drug-free sport in recent years, now stands to be banned for life.

Surely this marks a success?

Yes and no. These latest cases do appear to demonstrate the truth of the idea so beloved of drug-testing authorities around the world, namely that no one is safe to cheat. And it is certainly good news that these cases have been made public - in times past, neither might have seen the light of day.

That said, there is a lingering suspicion that what high-flying athletes who have been caught have been primarily guilty of is stupidity for putting themselves through the routine testing that now operates in the wake of competition with a substance inside them that is detectably incorrect.

The other worrying factor here is that both athletics and cycling have recently carried out major investigations which one might have hoped would act as a deterrent for other would-be offenders.

Who is winning the race between testers and cheats?

Those who cheat have always sought to stay one step ahead of the testers. Thus, for many years, competitors seeking to improve their muscle power and endurance have taken synthetic anabolic steroids, which mimic the action of the male hormone testosterone. Once reliable tests for steroids were established in the 1980s, cheats had to look elsewhere.

The trend nowadays is towards employing substances which occur naturally in the body such as testosterone, human growth hormone (hGH) and human chorionic gonadotrophin (hCG), which are harder for the testers to detect.

In recent years there has been a concerted effort to get hold of those seeking to improve performance by illegal means, and much of the progress has involved the devising of new tests. EPO, for so long indistinguishable from normal blood, can now be tested for. Scientists have also devised a means of detecting human growth hormone, although the International Olympic Committee has so far balked at the cost of introducing the reseach.

Which country is the worst offender?

The demise of Communism in Russia and East Germany revealed systematic state doping programmes for athletes in a wide range of sports. More recently, China has fallen under suspicion, particularly after a group of their women endurance athletes smashed a series of world records in 1993.

At the moment it is the US which is enduring the worst record for doping abuse in the wake of the Federal Investigation into the doping ring centred on the Balco lab in San Francisco.

Britain has had a steady number of offenders over the last 15 years, the most recent of whom, 100m runner Dwain Chambers, has just returned after a two-year doping suspension.

So who is doing all this testing?

Testing is carried out by national federations - in Britain's case, the process is overseen by UK Sport - under the umbrella organisation of the World Anti-Doping Authority, which was established six years ago by the International Olympic Committee and which operates independently under the chairmanship of IOC vice-president Dick Pound. More than 570 sporting organisations have signed up to the code that was adopted in 2004, which standardises dope-testing procedures and punishments. Most of the major sports are on board - although Fifa is still dragging its studs.

When did it all begin?

In the third century BC, according to the writer Galen, certain Olympic competitors tried to enhance their performance by consuming "the rear hooves of an Abyssinian ass, ground up, boiled in oil and flavoured with rose hips and petals".

Why not just let everyone take what they want?

That argument has been made regularly in the wake of the latest doping outrage, and it makes use of several anomalies in the current system. For instance, taking EPO is illegal, as is blood doping. But if you can afford to spend a few weeks training at altitude your blood will naturally manufacture extra red blood cells to help you cope. And that's legal. This argument goes along the lines that life isn't fair anyway, and feeds on assertions such as that made by Ben Johnson's coach, Charlie Francis, who maintains that a properly monitored drugs regime does no harm.

History records, however, that wholesale state-administered doping regimes such as that uncovered in East Germany before the unification of that country had an awful human cost, with at least one athlete dying as a result of the drug cocktails they were obliged to consume. Taking steroids increases the risk of cancer, and can lead to infertility, impotence and - for good measure - acne.

What does the future hold?

The future battleground is almost certainly going to be in the field of genetic engineering, as would-be cheats attempt to tweak their physical characteristics. Experiments at London's Royal Free and University College Medical Schools have bred mice to whom a substance called Mechano Growth Factor have been introduced. Their strength increases by 25 per cent within two weeks. For sufferers of muscular dystrophy, the research spells hope. For sport, it spells cheating.

Is the battle against doping being won?

Yes...

* The recent high-profile cases appear to demonstrate that no one is immune from being banned for doping, however famous

* Since its establishment in 2004, the World Anti-Doping Code has standardised dope testing and punishments

* Testing advances are beginning to have a profound effect

No...

* People will always find a way to cheat, and those with money can still buy smart methods which are currently undetectable

* The biggest breakthroughs against doping recently have been triggered by lucky breaks

* Genetic engineering is a nightmare that could evade all controls