Great Britain's London 2012 men's medley relay swimming team could receive retrospective bronze medals after Australia's Brenton Rickard tested positive for a banned substance.
Liam Tancock, Michael Jamieson, Michael Rock and Adam Brown originally finished fourth at the home Olympics.
Rickard raced in the heats of the event and a reanalysis of a sample he gave at the time has shown a banned diuretic.
In an email seen by the BBC, he has told his team-mates he was innocent.
He said the situation is "a living nightmare" and states stripping Australia of the bronze medal would be "grossly unfair and disproportionate".
A low concentration of potential masking agent Furosemide was discovered in the retesting of his A and B samples provided at the Games, which he claims must have come from contaminated over-the-counter medication taken in the week prior to the test.
The International Olympic Committee (IOC) is retaining samples from London 2012 for 10 years so they can take advantage of new technologies and unearth cheating.
More than 30 London 2012 medals have been reallocated because of retesting so far.
Should the IOC win their case against Rickard, which begins at the Court of Arbitration for Sport in Lausanne on Monday, the British quartet and Craig Benson - who swam in the heats - would be in line for an Olympic medal.
The home Olympics were largely disappointing for the British swimmers, with Jamieson's 200m breaststroke silver and bronze medals for Rebecca Adlington in the 400m and 800m freestyle their only successes.
It was half of the haul GB swimmers achieved at Beijing 2008 and head coach Dennis Pursley as well as performance director Michael Scott left their roles after London 2012.
"The biggest thing for me is that these things go through a process and they take time," Tancock told BBC Sport.
"I have the utmost trust that the right decision will be made whatever it is really, it's just a sad moment for swimming."
Britons have been retrospectively awarded medals on four other occasions in the past two years. In 2019, Goldie Sayers was given the 2008 javelin bronze and the 2014 men's four-man bobsleigh team were also awarded bronze.
In 2018 two other bronze medals were awarded, one to Kelly Sotherton for the heptathlon in 2004 and one to the Beijing 2008 women's 4x400m relay team.