With talk of building a society which is "modern and decent" through a "dynamic enterprise economy", by balancing "prosperity and fairness", Timms, treasury financial secretary, reassured many but inspired few. Then the crowd of around 60 members went off into different rooms, clutching brown envelopes, to discuss the policy documents sent by Millbank.

It is the eve of Labour's 100th birthday. The keynote speaker has wound up to polite applause. Nobody has mentioned the trade unions which set the party up or uttered the word "socialism". There will be discussions in small groups behind closed doors, and there has been no open, public debate.

The Labour party has a peculiar relationship with its history. It is both drawn by its symbolism but repelled by its significance; keen to establish an emotional link with its past but reluctant to admit any structural relationship with it. New Labour - that mixture of PR jingle and political construct - is still defined not so much by what it actually is, but by what it has abandoned.

The fact that the party has changed is, of course, both welcome and inevitable. It started the last century with two MPs and ended with the largest majority in its parliamentary history. All that has come between, from the birth, life and death of the Soviet Union to the globalisation of capital, via feminism, the ozone layer and the end of empire, has had a profound and fundamental effect on society that must be reflected in a party that wishes to lead it.

But for the best part of the century the fundamental tensions within the party have remained consistent. On the one hand there have been those who wanted to use the party's base among the working class as a vehicle for radical, social change; on the other those who wished to extend its appeal so that it could use its parliamentary presence to gradually negotiate reforms. In a sense it has been a phoney war. The two camps have not always been in conflict, have shared many basic values and in the broader scheme of things have always had more in common than divides them. But at times of crisis or opportunity the representatives of either side - be it Bevan and Gaitskell, Healey and Benn or Livingstone and Dobson - will square up for a conflict which threatens to split the party asunder.

"In other parts of Europe these two traditions have been the basis, broadly speaking, for two separate parties; social democratic and communist," wrote Hilary Wainwright in her book, Labour: A Tale of Two Parties. "In Britain, by contrast, the Labour party has united the majority of each tradition in one party."

For the most part these traditions have expressed themselves not so much as a battle of policies but of axioms. There is no point in having power unless you are going to use it to improve the livelihoods of those who support you, say one camp; you cannot do anything for those who support you unless you are in power, say the other. The arbitrator between these two truisms has traditionally been the membership which, through internal democracy, has always made its voice clear about how much its thirst for change might be quenched by the chance to taste power. Failure to hear this voice has been punished with low turnouts and a sharp decline in envelope stuffers, door- knockers and telephone canvassers as people who feel their support has been taken for granted or ignored stay at home. The result can be electoral defeat.

"Obedient ministers who tramp through lobbies strange to all they have ever said may preserve themselves from the prime minister's sacking," said Lena Jeger MP back in 1968. "But they do not protect themselves from a sacking in their constituencies, a sacking which may well not be deliberate but may come just because nobody turns up to drive the loudspeaker van."

Back at Norwich Labour club, the local trades council are showing a video about the Burston village school strike. In 1914 Annie Higdon, a teacher, and her husband Tom, her assistant, took on the local Norfolk clergy and squierarchy after their school was closed down by the authorities. The two socialists defied the law and opened up a strike school nearby which became a cause célèbre for the entire labour and trade union movement.

Through the grainy stills and personal accounts of pensioners who were pupils at the school emerges the glue that keeps these competing currents within the labour movement together - struggle. The arguing, campaigning and organising which forces progressive change - however modest - in favour of the many and challenges the power structure which serves the interests of the privileged few. "The Labour party is a moral crusade or it is nothing," said Harold Wilson in 1962.

With one foot in and one foot out of parliament the Labour party has, for the past century, provided an imperfect but constant conduit for the struggles taking place outside to be translated into legislative reform within it. Sometimes, as with the repeal of the poll tax or the miners strike of 1974, it was action on the streets that made the crucial difference. For the introduction of the NHS and the welfare state, the parliamentary route proved most effective. Although the two strategies have often appeared contradictory and antagonistic they have most often been complementary and symbiotic.

Or at least they were. For in this key sense Blairism does represent a break from the past. By distancing himself from the unions and sidelining internal democracy he leaves a vacuum between himself and the rest of the movement. What you are left with is not a campaigning party underpinned by the experience of struggle but an electoral machine driven by crude, majoritarian impulses. He represents not the architect of a social democratic party on the European model but of an American-style Democratic party. The resignation of Peter Kilfoyle and the breadth of support for Livingstone's independent candidacy suggest that concern over this goes beyond the traditional left.

And while none of this should detract from Blair's considerable achievements (like the minimum wage and devolution) or excuse his mistakes (like the harsh asylum regulations and his failure to deliver on freedom of information) it does present him with a vital problem which he needs to address within the next 18 months. His desire to broaden his support outside the party is eating away at his base within it; he risks becoming the head of a government without a body of activists to support him.