But while the bare outline of events is known, many of the finer details are still being thrashed out between the Palace, Downing Street and the Princess's family over the guest list, processions and involvement of the public.
The ceremony will take place in Westminster Abbey at 11am, and the Princess's coffin will be carried in procession from the Chapel of Rest in St James's Palace, where it is lying, out of public view. It is this procession which gives an opportunity for the public to display its grief, as well as the many planned tributes and silences around the country.
Around 2,000 guests will be invited to the service itself, though many more are expected to gather outside; family and friends of Diana, members of the Royal Family, and representatives of those organisations with which she was closely involved, such as charities.
As it is not a state funeral, which would usually attract heads of state or senior representatives of other countries, foreign representation is likely to depend on the Princess's links with a particular country. France's President Jaques Chirac has already indicated he would like to attend.
Some of the more formal trappings of a state funeral, such as a gun carriage to carry the body, seen at the funeral of Sir Winston Churchill in 1965, may well be included. And inside the church a catafalque - a tomb-like structure - will be constructed under the lantern to support the coffin during the service.
After the service, at which the Princess's family and the Royal Family will be seated in the front pews, the coffin will be taken in a hearse to Northamptonshire for a private ceremony in the family's Spencer Chapel. That procession will include members of the Princess's family and some members of the Royal Family.
The Spencer Chapel, which houses the remains of 20 generations of the family, lies in the north-east corner of the St Mary the Virgin church in the village of Great Brington. It was built as a private family mausoleum in 1516 on the instructions of one of Diana's ancestors. If, as thought likely, family tradition is observed, Diana's ashes will be interred after cremation.
The route of the hearse to Northamptonshire will be announced later, along with further details about the service, including the expected congregation and participating clergy. A spokesman for the Archbishop of Canterbury, who may take the service, said his office was in contact with the Lord Chamberlain's office and the Abbey, where the senior cleric is the Dean, the Most Reverend Wesley Carr.
Not all members of the Royal Family will be attending the interment, instead returning to Balmoral soon after the service, though it was unclear if this would include the young princes.
Meanwhile, four books of condolence were being opened at St James's Palace as a focus of mourning for the crowds of people who began to gather there yesterday.
The details released so far indicate that, as befits such an unusual Royal personality, the ceremony will be different from either a state funeral, a Royal "ceremonial" funeral such as the Duke of Edinburgh may have, and a private royal funeral. As a Buckingham Palace spokeswoman said: "This is a unique funeral for a unique person."
A state funeral is usually reserved for sovereigns alone although, on rare occasions exceptionally distinguished people - such as Lord Nelson, the Duke of Wellington, and in 1965 Sir Winston Churchill - have been honoured.
A state funeral is one approved by the Monarch and one for which funds have been voted by both Houses of Parliament. Diana's, by popular demand, seems likely to be such an occasion in all but name.
For the Queen, the discussions are being handled by The Lord Chamberlain, Lord Airlie, and his staff including the comptroller and assistant comptroller, as well as other Royal officials.
The Lord Chamberlain, the head of the Queen's Household, is likely to be a prominent figure at the funeral, close to the Queen and carrying his staff of office. As senior member of the family, Earl Spencer, Diana's brother, is representing her side. Unnamed senior officials in Downing Street will represent the Government.