The Lance Armstrong scandal left a huge gap in cycling's record books and further tainted the sport in a year when Britain experienced Olympic bliss in the wake of Bradley Wiggins' Tour de France title.
Armstrong was banned for life and stripped of his record seven Tour de France titles after the U.S. Anti-Doping Agency (USADA) uncovered what it said was the "most sophisticated" doping programme ever found.
It was, however, a vintage year for British cycling as they won their maiden Tour through Wiggins and scooped 12 medals at the London Olympics.
But the feelgood factor for the sport was shortlived as on Aug. 23, Armstrong announced he would no longer fight doping charges after failing to have the process blocked by a judge.
His decision prompted the U.S. Anti-Doping Agency to announce the Texan would lose his Tour titles from 1999-2005.
It was not until mid-October, however, that the extent of Armstrong's fraud was exposed when USADA published a 1,000-page report featuring testimonies from former team mates incriminating the American, a cancer survivor who went on to dominate the sport's greatest race more than anyone else.
His accusers said that with Armstrong effectively in charge, hotel rooms were transformed into blood banks, doctors were paid off and riders were warned about tests in advance.
Faced with the weight of evidence from Tyler Hamilton, Floyd Landis, Jonathan Vaughters and more, the governing UCI had little choice but to ratify USADA's decision and leave a blank in the record books, with president Pat McQuaid saying that Armstrong had "no place in cycling".
As a result, Armstrong, who has always denied any wrongdoing, was dropped by sponsors such as Nike and even had his name dropped from the cancer foundation he himself created.
Rabobank, a long-time sponsor of the sport, also left cycling because of the negative effects of the Armstrong scandal.
With the sport on its knees, the UCI set up a commission to look into USADA's decision and into allegations that the governing body had failed to do everything it could in the fight against doping.
By that time, Wiggins was still trying to come to terms with the fact he had won the Tour.
The kid from the London district of Kilburn had an outstanding season, winning the Paris-Nice, Tour de Romandie and Criterium du Dauphine week-long races before becoming the first Briton to win the Tour de France as Team Sky's obsession with details paid off.
Wiggins built his success on his impressive time-trialing abilities and benefited from his team's support in the mountains, with Chris Froome sacrificing his own chances for his leader but still finishing second overall.
The race was not the most spectacular in recent Tour history but it rewarded a rider and a team who left little to chance.
The year 2012 was also special for Tom Boonen as the Belgian won a record-equalling fourth Paris-Roubaix title, snatched a unique second Roubaix-Tour of Flanders double and became the first rider to achieve the Flemish cobblestones quadruple of E3 Harelbeke, Gent-Wevelgem, Tour of Flanders and Paris-Roubaix.
Alberto Contador made his much-awaited return from a doping ban just before the Tour of Spain (Vuelta), which he won after one of his trademark solo efforts that unsettled eventual world number one Joaquim Rodriguez.
The Spaniard, one of only five riders with titles in all three grand Tours (France, Italy, Spain), made his move when nobody expected it and then hung on for the red jersey to become the third grand tour winner of the year after Wiggins and Giro champion Ryder Hesjedal of Canada.
Spain's Rodriguez finished the year as world number one but there was nothing he could do to prevent Belgium's Philippe Gilbert becoming world champion thanks to a brutal attack in the final climb in Valkenburg, Netherlands.
Gilbert succeeded British sprinter Mark Cavendish, who had a rough year, being reduced to a domestique role on the Tour de France to help Wiggins claim the title although he still managed to win three stages to take his tally to 23.
Cavendish left Team Sky to join Omega Pharma-Quick Step as the Manxman bids to one day beat Eddy Merckx's stage-wins record of 34.
He suffered a further low as Britain failed in their bid to take him to a much-awaited victory in the road race at the Olympics. Britain were outfoxed by the Kazakh Alexandre Vinokourov, who prevailed thanks to a bold attack which saw the victory of old school cycling.
Britain bounced back from the early Games disappointment, reasserting their domination in Olympic cycling with another awe-inspiring medal haul on the track and Wiggins' terrific victory in the road time trial.
The squad took the velodrome by storm in a spine-chilling atmosphere with Jason Kenny and Chris Hoy leading the charge with two golds while the pursuit teams shattered world records as Britain equalled their Beijing record of seven titles.
Britain's rivals were generally left picking up the crumbs.
The team, led by British Cycling director of performance David Brailsford, grabbed a total of 12 medals across all disciplines, eight of them gold, while no other delegation managed more than one title.
Australia were spared total embarrassment when Anna Meares beat British media darling Victoria Pendleton 2-0 in the individual sprint final on the day Hoy prevailed in the keirin to become Britain's most successful Olympian.
Hoy has seven Games medals, six of them gold, which put him ahead of Wiggins on 'gold difference' and took him past rower Steve Redgrave's previous record British tally of five golds.
It was a year to forget, however, for the Schleck brothers, who were expected to give Wiggins a run for his money on the Tour de France.
Andy did not even take part after sustaining a hip injury in June that ruined most of his season while his older brother Frank was withdrawn form the race by his Radioshack-Nissan team after testing positive for a banned diuretic.
Doping was not the only issue cycling faced in 2012 as investors wanting to secure the sport, as well as several teams looking for a larger piece of the pie, opened talks to launch the World Series of Cycling, 10 four-day grands prix all around the world organised in a possible joint venture with the UCI.
How it can fit in a very busy calendar with cycling's historical races is an unanswered question.
In women's road cycling, Dutchwoman Marianne Vos confirmed she was the female version of the great Merckx, winning the world and Olympic titles.
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