Leading article: A marriage that opens the way for a modern monarchy

It will be in many ways a different country that greets Prince William and his bride tomorrow

Preparations for the royal wedding have advanced with the stately sense of purpose this country does so well. As the day has neared, so the pace has accelerated. In the streets of London, displays of flags and good wishes have multiplied by the day. The final sprint has seen the flowers – and the trees – installed in the Abbey. That speciality of royal occasions – cast-iron security exercised with the light touch of discretion – is almost in place. After yesterday's rehearsal, the cavalry and the carriages know where to go. So, tomorrow, with expert direction, will the crowds. Almost 30 years after the nuptials of Charles and Diana – and all that followed – we have to evince just a little surprise that a Prince's wedding is again exerting its magnetic power.

Yet it will be in very many ways a different country that greets Prince William and his bride: more diverse, more tolerant, less respectful of convention, perhaps less confident. In some ways, too, it will be a different monarchy that embraces Kate Middleton. The traumas of these three decades, which brought separation, divorce, scandal and the untimely death of the Princess of Wales, have left their mark. The Queen herself described 1992 as her annus horribilis, but there was more, much more, to come.

And while the country may have rediscovered a taste not just for reassuring pageantry, but for the solidity that the institution of the monarchy still represents, the contrasts between the wedding of July 1981 and that of April 2011 are at least as telling as the similarities. Charles's life had been more traditionally royal, more protected, than that of his son. His choice of bride was severely restricted: aristocratic birth and virginity still came into it. And with hindsight, the wedding, at St Paul's, manifested much of the excess of those years: the dress, the train, the procession, the guest list, the banquet. As for the country, the street parties held that day have passed into many an adult memory: loyalty to the Crown was still mostly a given.

William's childhood was hugely privileged, but – probably thanks to his mother – not isolated. His experience of school and university was exclusive, but shared. He lived openly with Ms Middleton – a well-to-do and privately educated commoner, but still a commoner – before embarking on marriage. As a search-and-rescue pilot, he has a "proper", and highly skilled, job. His life has already intersected with those of his future subjects infinitely more often than his father's ever has.

What is more, this marriage will bring together two grown-ups whose wild oats are sown and whose wedding celebrations, while far from a cut-price trip to the register office, will recognise today's more austere public mood. That the Prime Minister's guest attire became a talking point itself hints at our socially shifting times.

Westminster Abbey, of course, even on a late spring day, will inevitably conjure up darker memories; memories of that September day when, only 15, William walked with his brother behind his mother's coffin. The funeral of the Princess of Wales, with its lavish outpouring of public emotion, the bitter reproaches of her brother from the pulpit, and the cold formality of the response from the Palace, betrayed a monarch more remote from the people than at any time in her reign – and a monarchy whose durability could no longer be presumed.

That crisis was gradually overcome. Now, the marriage of Prince William and Kate Middleton opens the way for the monarchy to continue into a new generation, but also – we hope – for the royal couple to influence its evolution into a simpler, less hidebound and generally more modern institution, more closely attuned to the changing social climate of the 21st century.