The brothers finally have a sister.

Not before time. It's taken the TUC 144 years to elect its first female leader. With female unemployment at a 25-year high and women shouldering 70% of the Coalition's budget cuts, she's arrived in the nick of time.

Frances O'Grady isn't exactly a household name. Yesterday Wikipedia could manage only two paragraphs on her but she's the real deal. Her dad was a British Leyland shop steward at Cowley and her grandfather a founder member of the Irish Transport & General Workers Union.

In her own time at the T&G she campaigned for the national minimum wage and equal pay for women. And at the TUC she has laboured to rid trade unionism of its blokey image, arguing that the leadership should better reflect the six million membership, which is now 50% women. Many are in part-time, low-paid, insecure jobs. As a single mother herself, she's also enraged that the recent debate over the public sector is still underpinned by the myth that women work for pin money and can manage on a worse pension, presumably because "hubby can provide".

So this could be a seminal moment. In Scotland women came in with the bricks of the trade union movement. In fact, back in 1897 the very first STUC secretary was Margaret Irwin, the daughter of a sea captain. The first women's conference was held in 1926 on the eve of the General Strike and women led campaigns for the family allowance (child benefit), youth employment and the teaching of working-class history to schoolchildren. However, at the workface, regardless of official union policy, trade unionists were often as chauvinistic as bosses. When I applied to jobshare 25 years ago, one union rep seriously suggested I should choose between my job and my family or accept a demotion.

Nationally, it looked as if the old cloth cap and smoked-filled rooms image of trade unionism would be consigned to history with the election in 1985 of the glamorous Brenda Dean to lead Sogat, the biggest print union, but it was a false dawn. Today 15 of the 58 unions in the TUC may be led by women, including Michelle Stanistreet of the National Union of Journalists, but, like the political parties, all the major unions continue to be led by middle-aged men.

In 2010 Ms O'Grady realised that British trade unionism had reached a pivotal moment. The challenge was to capitalise on mounting distress about the dismantling of public services and forge an alliance between trade unionists and the general public. But the TUC's All Together for Public Services campaign has been slow to gather momentum. Initially the Labour Party was in disarray and schizophrenic about strike threats. And old-style abrasive union leaders, such as Len McCluskey of Unite, made it too easy for David Cameron and the right-wing tabloids to caricature the unions as wreckers, undermining the public interest. Frequent references to the "Winter of Discontent" played on the public's insecurity.

Hopefully, Ms O'Grady's soft voice and toothy grin will be disarming. Mr Cameron has difficulty dealing with women professionally and it's been predicted that she could be his "nemesis". Somehow, she needs to retain the threat of strikes, while employing a strategy designed to win over the general public. Recent events will help. People now realise that greedy bankers and tax dodgers, not home helps and classroom assistants, pushed the UK economy to the brink of meltdown. Her immediate objectives must be to persuade the Coalition to stimulate the creation of real jobs for the young unemployed and halt the slide in the living standards of the low paid and "squeezed middle". In the right hands, this could be trade unionism's big moment. Voters who see their public services being shredded can make common cause with public sector unions and those working for private sector contractors, who have watched their work dry up. Brendan Barber has been a good TUC General Secretary but potentially Ms O'Grady could be a better one.