Chris Huhne's resignation is the third of David Cameron's Cabinet since the election of May 2010. Two have these have been Liberal Democrats and all three have involved matters of personal judgement, rather than ministerial incompetence.
The first scalp came within a month of the coalition being formed, when then Chief Secretary to the Treasury David Laws was forced to stand down after he was found to have wrongly declared MPs expenses. He'd wrongly claimed around £40,000 in rent for a flat owned by his partner. The tragedy for Laws was that he'd done this to avoid being outed as gay, and a parliamentary inquiry subsequently found that while Laws had clearly acted improperly, he hadn't done so for financial gains. David Laws's resignation caused a mini-reshuffle less than a month into the life of the government. Nick Clegg has been open about his desire to get Laws back into the Cabinet at some point.
Liam Fox was the second casualty, this time over improper access by his close friend Adam Werritty to ministerial offices and meetings. The drip-drip of revelations began with the claim that Werritty had House of Commons business cards despite not being an official staff-member in Parliament. The allegations continued, including Werritty's attendance on ministerial trips, Whitehall meetings and dinners with other lobbyists. Fox's resignation finally came after it emerged that right-wing zionists had been bankrolling Werritty.
Chris Huhne's resignation comes ahead of his appearance in court on February the 16th. He'll stand in the dock alongside his estranged wife Vicky Pryce. She is accused of accepting speeding penalty points on her husband's behalf in 2003. Both are charged with perverting the course of justice, a serious offence which can carry a jail sentence.
FULL COVERAGE OF HUHNE'S RESIGNATION
Apart from the three Cabinet members to lose their jobs, three very junior ministers have left the government. Tory MP Aidan Burley lost his job a ministerial aide after helping to organise a Nazi-themed stag party, and Adam Holloway and Stewart Jackson both left the government after they rebelled on a Commons vote calling for a referendum on the EU.
But not every minister to find themselves in difficulty has resigned, as the photos below reveal, there have been some canny survivors: