Before the St Paul’s Cathedral service that confirmed her on Wednesday as the first female archbishop of Canterbury, Dame Sarah Mullally repeated a proverb that has become something of a personal mantra: “If you want to go fast, go alone; if you want to go far, go together.” In an Anglican communion that remains bitterly divided, rancorous and unsure of its public role, an invitation to partnership and collaboration hit the right note. The formidable task now for Dame Sarah will be to provide the leadership to make it happen.

As a state-educated former NHS worker who rose to become England’s chief nursing officer, the 106th occupant of St Augustine’s chair is a very different proposition to Justin Welby, her Old Etonian predecessor. But many of the challenges she confronts remain the same. Her immediate priority must be to end the cycle of failure in dealing with historical abuse in the church, which has led to a collapse of trust in parishes and ultimately forced Mr Welby’s resignation.

After years of prevarication, a general synod next month will discuss proposals to finally outsource safeguarding to an independent body. Reform must not be delayed any longer. At the same meeting, Dame Sarah will need to reassure LGBTQ+ Anglicans that the path to same-sex marriage in the church has not been permanently closed down after bitter opposition from traditionalists. In the years ahead, progress may spell trouble for its relations with conservative members of the worldwide communion. Ultimately, however, unity without true inclusion is a hollow concept.

Beleaguered and short-staffed local parishes have also felt neglected and undervalued, as the Anglican hierarchy has resisted calls to boost clergy numbers on the ground. But it is in the public square that Dame Sarah may face the defining test of her period in office. Hearteningly, it is already clear that she will use her platform and experience to highlight the crisis in social care – a national scandal that Westminster has abjectly failed to address. But she also enters Lambeth Palace at a time when new challenges are emerging for the established church.

As pews have steadily emptied over the decades, secularisation was always the fundamental challenge facing any incoming archbishop. Co-option rather than marginalisation is the urgent issue now: the rise of Christian nationalism is threatening to misrepresent the faith in the name of an aggressive nativism.

September’s “Unite the Kingdom” march led by Stephen Yaxley-Lennon (AKA Tommy Robinson), in which far-right activists carried crosses and chanted “Christ is king”, has provoked a long bout of episcopal soul-searching. Though some bishops, including the Rt Rev Arun Arora, spoke out against a distortion of Christian values, there has been a notable lack of coherent direction from the top. For her part, Dame Sarah has suggested that in a divided society “people are frightened for lots of reasons, and often that then presents in ways that, for other people, may feel threatening”.

Between now and a general election that could deliver power to xenophobic forces claiming to protect Christian culture, a more robust approach than that will be required from the new archbishop. As the first woman to become the spiritual leader of the Anglican communion, Dame Sarah embodies a message of diversity and inclusion to be celebrated. In a politically febrile period, those values will also need to be stoutly defended, both inside and outside the church.