A week ago, the 58-year-old former energy secretary pled not guilty to perverting the course of justice but just before his trial was due to begin at Southwark Crown Court, he dramatically changed his plea and admitted trying to dodge a driving ban by getting his former wife, Vicky Pryce, to accept penalty points for speeding.
She sat impassively next to him in the dock as he admitted his guilt.
Outside court, Huhne, released on bail, announced he would be standing down as an MP; his political career in tatters. He will be sentenced later but can expect a prison sentence of up to two years.
Earlier, the judge, Mr Justice Sweeney, told him: "You should have no illusion whatsoever as to the sort of sentence you are likely to receive – understand?" The ex-minister nodded.
The development surprised Westminster, where Huhne had been confidently telling friends he expected to be cleared. As yet, there is no sign he will hand back the £17,000 he received for quitting the Cabinet last year.
Now, Nick Clegg, who said he was "shocked and saddened" by his colleague's admission, faces the possibility the LibDems could lose the Hampshire seat Huhne held on to by just 3864 votes at the General Election.
The Conservatives will be hoping to take the Eastleigh marginal but UKIP also fancies its chances; its leader Nigel Farage is considering standing.
The claims that Huhne had sought to get round a driving ban first emerged in 2011, a year after he left Ms Pryce, 60, an economist, for Carina Trimingham, 45, a PR adviser, who worked on his LibDem leadership campaigns in 2006 and 2007.
Dismissing the speeding allegations as "simply incorrect", he stepped down from the Cabinet last year when he was charged. In his resignation letter to the Prime Minister, he told David Cameron he would mount a "robust defence".
Because of his change of plea, his bid to get the case against him thrown out can be reported for the first time.
The politician's legal team, led by top QC John Kelsey-Fry, sparked days of legal argument with an application not only to get the case dismissed but also to have the trial stayed because of an abuse of process.
Mr Kelsey-Fry, who reportedly charges up to £20,000 a day, branded the prosecution's case "at best gossamer thin", claiming the evidence was all circumstantial.
However, the prosecution insisted it clearly pointed to the former minister as the person behind the wheel. Texts read out during legal arguments showed pressure on Huhne from his son Peter. In June 2010, Peter Huhne texted his father: "We all know that you were driving and you put pressure on mum. Accept it or face the consequences. You've told me that was the case. Or will this be another lie?"
"Actually Peter, I've got no intention of sending mum to Holloway for three months," Huhne replied.
His son texted back: "Are you going to accept you're responsible or do I have to contact the police myself and tell them what you told me?"
The prosecution said Huhne, an MEP at the time of his offence, had a history of speeding and, with nine points, was already in danger of losing his licence.
At 11.23pm on March 12, 2003, having returned from Strasbourg, his BMW was clocked on the M11 at 19 mph above the 50mph speed limit. Forms returned to Essex Police said Ms Pryce had been driving; and she was given three penalty points.
Prosecutor Andrew Edis QC said all the evidence pointed to Huhne driving and it was unlikely Ms Pryce would have made an 80-mile round trip from London to collect her husband.
Mr Kelsey-Fry said Huhne could not receive a fair trial because he was only confronted with the allegation eight years on, forms had been destroyed and he had received a deal of adverse media publicity.
Legal arguments took days but despite his legal team's effort, the judge ruled against both applications, neither dismissing the case nor granting a stay because of an abuse of process.
Today, the trial of Ms Pryce, who denies the charge against her due to marital coercion, is due to begin and is expected to take a week or so.