It is traditional that the father of the bride pays for his daughter's wedding. But when it comes to royal nuptials custom favours the commoner.
The cost of Prince William and Kate Middleton's union will run into millions and will be largely met by public funds. The bulk of this expense will go on the huge security bill for the occasion.
The announcement of a wedding adds another red letter day to a police diary already overflowing with costly events. One member of the Metropolitan Police Authority, Scotland Yard's board of governors, warned that budgets were already tight.
Green politician Jenny Jones said a compromise could see the Windsors contributing to the cost of policing.
She said: "In this age of austerity, it's unrealistic to expect the taxpayer to pay millions for policing a wedding, however beautiful. We can keep costs down by making it a low-key event or the Royal Family can contribute. That would seem the fairest solution."
The Queen and the Prince of Wales will be expected to pay their share of the costs of the pageantry and private parties. In the recent historic deal over the future public funding of the Royal Family, exceptional provision was made for supporting the Queen's Diamond Jubilee.
In the wake of last month's Comprehensive Spending Review, the Queen agreed to cut total Royal Household spending by 14 per cent in 2012-13.
It was also announced that Buckingham Palace had cancelled its £50,000 (NZ$103,366) Christmas party. The Department for Culture, which pays £15m a year towards the upkeep of royal palaces, has already demanded that maintenance costs for the palaces and royal travel costs be reduced by 25 per cent.
The Royal Household and the Government claimed that the new deal over a sovereign grant would save the public money. An additional financial burden - such as a Royal wedding - makes such a claim sound a little hollow. It also raises the prospect of the Queen going back to Parliament to ask for another hand-out.
Graham Smith, a spokesman for the anti-monarchist group Republic, said: "William is not the head of state; there is no guarantee he will ever be head of state. This is a private occasion which I'm sure the Palace will want to milk for maximum PR effect. It is not for the taxpayer to pay for any part of this event; the Windsors must cough up."
Securing the Royal Family, VIP guests and key locations will be at the centre of the expensive police operation. But monitoring thousands of onlookers who will surround the venue and line the route is likely to be the most high-profile police responsibility.
In 1981, thousands of police officers and members of the Armed Forces lined the route of procession of Diana, Princess of Wales, from Clarence House.
Up to 600,000 people gathered in central London and the spectacle was watched by some 750 million people worldwide.
In 2005, officers from the Met and Thames Valley Police oversaw the marriage of Prince Charles and Camilla Parker-Bowles in Windsor.
Officers from specialist squads including royalty protection, diplomatic protection, CO19 and Special Branch were involved, as well as beat teams.