Part one: How bad is it for the government?

It was an "extremely difficult day". The opposition claimed there had been "colossal errors of judgement". Others pointed to a government that had "failed", had "lost control", was in a state of "political shambles", surrounded by a "political disaster of the first magnitude".

The descriptions sound like the chaos that engulfed the government last week: crises - first at Northern Rock, then the Revenue and Customs fiasco - that deepened the gloom in Numbers 10 and 11 Downing Street. In fact, they come from September 16, 1992, the day remembered as "Black Wednesday" and the date the Conservatives lost all claim to be a competent government.

For Black Wednesday now read "Black November", the period after the election that never was, when a decade and more of New Labour's plans to replace the Conservatives as the party of government and economic competence all but collapsed.

On Friday afternoon, two Labour MPs at Euston station, en route to their constituencies, said that "unless we get a grip, it will be a black December, a black Christmas and dark new year ahead".

And were they hopeful a quick fix to end the crisis would be found? The two answers were brief. "No."

When Gordon Brown returns to London from the Commonwealth conference in Uganda he will fly into what one Tory MP called "the open season on Brown and Darling", a period of unrestrained criticism where everything that has gone or might go wrong will be laid at Downing Street's two main doors.

This is less a case of a plot to inflict further damage on Brown and Alistair Darling, more a realisation that because the government is perceived as having lost the plot, the narrative in Westminster has become one of a government stumbling from one crisis to the next.

Comparisons to John Major and Norman Lamont from 1992 are being fended off by Brown loyalists, who insist that since the Labour conference in Bournemouth Brown has been dogged by bad luck, and that failed competence is an unfair characterisation of events.

"Major and Lamont lost people their homes and their livelihoods. That hasn't happened here and isn't going to," said one adviser. Others remain less certain.

Labour's leader in 1992, John Smith, called Major and Lamont "the Laurel and Hardy" of British politics, adding: "Another fine mess they've got us into." The mud stuck as the scale of events on September 16 unfolded. By the end of Black Wednesday, the Bank of England had made the largest intervention in the currency markets in its history. The bank had sold more than £15 billion of its reserves over two days and interest rates had jumped from 10% to 15% before Lamont pulled Britain from the ERM. The final cost to the UK taxpayer was said to be between £3bn and £4bn.

At the beginning of last week, before the fiasco of the two lost CDs at HMRC emerged, doubts were beginning to surface about the scale of the Chancellor's intervention in Northern Rock and his decision to use £23 billion of taxpayers' money to bail out a commercial lender.

Nigel Lawson, chancellor under Margaret Thatcher, believed there were only two types of chancellor: the kind who failed in the job and those who got out while they could. Darling is neither. He's been in the job a matter of months, and even a hint at resignation would be refused by Brown. Darling is supposed to be the extension of Brown's decade at the Treasury; his successor isn't supposed to fail and let prudence down.

But when Darling told the Commons that personal details of 25 million people had been lost in the post because a junior official at HMRC failed to follow procedure, the prime minister's armour looked damaged, his arsenal of options non-existent.

In the run-in to the Labour conference, where rumours of an early poll were never denied, it was said that Brown would fight the election on competence. His decision to not go for an early test of his authority, he said, would allow him to be judged on his record. There would, he insisted, be time for his vision to be understood.

Only weeks from that statement, the vision looks blurred, and the issue of competence is one any member of the Cabinet would find hard to defend.

Tony Blair had many "worst weeks yet". For "Teflon Tony", trouble, unless it was Iraq, didn't stick around long. As a skilled actor possessed of charm, he could shrug and smile his way out of a crisis. And when gravitas was needed, he could point to Brown as the dour-but-trustworthy face of economic competence.

Darling, as an extension of Brown at the Treasury, does not do that kind of job for the prime minister. So as the open season on Brown moves into December, and with every possibility the Tories will continue the attack into the new year, there's no haven in sight.

Marooned in uncertainty and accused of following the Tories' lead on inheritance tax, the Brown bounce has evaporated in opinion polls that in one case (Channel 4's YouGov poll) put the Tories past the critical 40% mark, helped by the lost discs farce. Labour were left struggling on 32%.

Brown is said to be seriously confused at what has happened to him since the summer. In Uganda he tried to mention what good work the government was doing - he talked about floods, terrorism, foot and mouth - and only deepened the perception that the summer's "Brown bounce" had been a mistaken blip in Labour fortunes. Once the hard reality of running the country kicked in, the questionmarks over Brown's ability to slot into the top job - the doubts regularly mentioned by key Blairites anxious that Blair's successor should be anyone but Gordon - appeared to be confirmed.

Brown's Home Office looks no different to Blair's, prone to errors on the scale and effectiveness of immigration control; Brown's authoritarian persona surfaced as he forced a U-turn from his new security minister, Admiral Lord West, on extending the period of detention without charge from 28 days. Even Blair's former attorney-general, Lord Goldsmith, and director of public prosecutions Ken Macdonald, voiced doubts about the need to go beyond 28 days.

Perceived as losing the plot, the open season on Brown is widening. Axes have been resharpened from previous encounters with the Treasury, especially the "military bastards" (Blair's biographer, Anthony Seldon, says this is how Brown referred to the generals), said to be loathed by Brown as chancellor.

They took advantage of the Northern Rock and HMRC crises and kicked the government when it was down. The line-up of lords who took it in turn to describe Brown as unsympathetic when it came to the Ministry of Defence's needs had their grievance rubber-stamped by General Sir Mike Jackson, who said the MoD's difficulties hadn't happened overnight, but had been part of a pattern of the past decade. The target of Jackson's comments? Gordon Brown.

What happens now? For one former Labour minister, that depends on how the Labour benches divide themselves in this crisis. He said: "If it's just optimists and pessimists, we'll ride this out in the hope that some good days lie ahead for us, some bad days for Cameron. But if we divide into defeatists and loyalists, then there's trouble ahead. We'll have a divided party, with some anxious that Gordon stays and others hoping he'll go in order to save us all. There may, to put it bluntly, be some madness ahead."