The Japanese people have been remarkably forgiving of their politicians down the years, re-electing men (as politics in Japan is usually a male preserve, and it is men who find themselves in trouble) who have been caught out having extramarital affairs, abusing political funds, accepting backhanders or simply being incompetent at their jobs.

When it was done at home, before a primarily Japanese audience, it could be shrugged off as an indiscretion. But with the nation being told to tighten its belt and accept rising unemployment, reduced wages and at least another 12 months of economic uncertainty, Shoichi Nakagawa appeared before the world's press and humiliated Japan.

Ordinary Japanese describe his performance as 'shameful' or 'disgraceful'. There is no shrugging of shoulders this time.

'For the Japanese people, it is a very fortunate thing that he has resigned,' said Tetsuro Kato, a professor of politics at Hitotsubashi University. 'He had no one in the party to defend him - only Prime Minister Taro Aso.'

Mr Nakagawa's resignation on Tuesday evening was inevitable, but Mr Aso's efforts to shield his close ally, not to mention the earlier decision to promote him to the cabinet, have raised new questions about the political nous of a leader already grappling with single-digit public support ratings.

While the prime minister struggles on to inevitable electoral doom, or chooses to fall on his sword, Mr Nakagawa has time to ponder his past and his future.

Born in Tokyo in 1953, he attended the elite Azabu High School before graduating from the law faculty of the University of Tokyo. From there, he took a job at The Industrial Bank of Japan, where he rose through the ranks until his father committed suicide. As is often the way in Japanese politics, he assumed his father's political legacy and seat in Hokkaido, and was elected to the Diet.

Quickly earmarked as a high-flier, he became minister of agriculture and fisheries in 1998, before prime minister Junichiro Koizumi selected him as minister of economy, trade and industry. Another stint at the agricultural ministry and as chair of the LDP's Policy Research Council were followed, in September last year, by Mr Aso naming Mr Nakagawa - a long-time ally - as minister of finance, and minister of state in charge of financial services.

At the same time, he had built himself a reputation as a blunt speaker - he once described North Korea as 'a scary country' - and very much a dyed-in-the-wool conservative. The rumours of a drinking habit were also beginning to gain credence.

By the time of his final cabinet appointment, the global economic meltdown was already well under way, and in November, he seemed in command of the facts and figures as they related to the Japanese and world economies. He reeled off the government's plans for addressing falling consumption and declining exports. He batted aside fears that the government would not be up to the task of reversing the increasingly alarming slide. He was slick, professional, informed and in control.

It was, however, a lunchtime meeting, and the only drinks on the table were water. According to people who have spent time with him after the working day has been done, he is a completely different creature when the water is changed into wine. Or shochu spirits, reportedly his favourite tipple.

Drinking some years ago with a small group of people in a Ginza bar known as a favourite after-hours hang-out for politicians, one of the participants recalls Mr Nakagawa simply selecting one of the six as his drinking partner, in very much the same way as a long-distance runner employs a 'pace runner' to keep the speed up.

To anyone who has experienced Mr Nakagawa's drinking habits, the outcome was inevitable. The minister left the bar in fine fettle; his drinking partner had to be bodily helped into a taxi.

The Japanese like to drink, of course, and nothing Mr Nakagawa did in his own time was ever commented upon in the media or among the public. But when it affected his performances in public, he laid himself open to criticism.

In 2000, after winning an election, he was famously unable to draw a round eye on a daruma doll, a traditional sign that a wish has come true. Instead, the mark ended up in the shape of a teardrop.

In television footage taken in 2006, at a press conference for the LDP's policymaking board, Mr Nakagawa is shown stumbling as he gets out of a government car, a minder walking behind him as he walks unsteadily through the foyer, and then red faced as he removes his tie at the start of the meeting.

Seated beside then prime minister Shinzo Abe, he mutters, mumbles and leaves long pauses between his comments. His gesticulations become more theatrical. Mr Abe looks at his colleague out of the corner of his eye, crosses his arms across his chest and leans back until the rambling delivery comes to an end.

In another incident, in October last year, Mr Nakagawa turned up 15 minutes late to a morning news conference and failed to detail measures on stabilising the markets - and stocks sank to their lowest level since the economic bubble burst in 1990.

In a financial policy speech to the upper house in January 28, he misread no less than 26 parts of his prepared speech; a ministry official explained at the time that he was 'feeling bad due to a cold'.

By then, it was already apparent to the rest of the party that one of the government's top spokesmen on key policy issues had a drinking problem.

Former prime minister Yoshiro Mori, speaking after the debacle in Rome that sealed Mr Nakagawa's political fate, revealed that he had been warned before about his behaviour.

'As he really loves to drink, I advised him in the past to be careful about his drinking,' Mr Mori said on a television programme on Sunday morning, the day after Mr Nakagawa's speech in Rome.

The footage of that press conference has been seen around the world, and was the most viewed clip on the Japanese YouTube site.

Mumbling, red faced and slurring his answers to reporters' questions, Mr Nakagawa did himself no favours by later claiming that he had been tired and taken too much cough medicine.

With the country facing the worst economic crisis since the end of the second world war - and figures showing that Japan's economy contracted at the fastest pace since 1974 in the third quarter - there was inevitably a chorus of demands that Mr Nakagawa resign for bringing shame on the nation.

'His father was a drinker as well, but not in the same way as his son,' Professor Kato said.

'This will be a huge disappointment to him because he must realise that he now has no support within the LDP, and realistically, it will be impossible for him to ever recover the situation.

'He has literally drunk away the prime ministership.'