It has long been held by constitutional experts that the British public would never tolerate Queen Camilla. The declaration by the Prince on Thursday that he would not remarry might seem to set the seal on any such possibility once and for all.
Yet there is nothing in English law which would prevent him marrying Mrs Parker Bowles and remaining King. Furthermore, in our unwritten and thus extremely flexible constitution, what is acceptable behaviour from the royal family seems to be constantly being extended: who would once have dreamt of an unhappy royal couple, let alone a royal couple publicly confessing their adulteries? What was unthinkable 10 years ago is now a fact of national life.
Might not that one day be the case with Camilla? The law does not forbid it. The 1701 Act of Settlement requires only that the monarch should not marry a Roman Catholic. Further rules introduced by George III in the Royal Marriages Act of 1772 state that no royal marriage can take place without the consent of the sovereign.
Neither of these laws would prevent Charles from marrying his mistress. Firstly, Mrs Parker Bowles, whilst once married to a Catholic, is an Anglican. Secondly, Charles would not in the event have to ask his mother's permission to re-marry.
"It is a little-known fact of the provisions of the Royal Marriages Act that once the heir is over 25 it would require only the consent of Parliament, and not the active involvement of the sovereign", said Michael Nash, a senior lecturer in law at Norwich City College and writer on constitutional affairs. "The Privy Council would be convened, and given the mood of the country it is inconceivable that Parliament would object."
Charles would, however, experience difficulty if he wanted to marry in the Church of England. But he could always marry abroad, or, like the Princess Royal, remarry in Scotland.
Even though the Church's reluctance to marry the couple would extend to carrying out their coronation, the reality is that the Archbishop of Canterbury does not have to crown the monarch for the coronation to be legitimate, just as the Queen does not have to be present to open Parliament.
"Everyone assumes that a coronation is essential for a monarch to reign, but basically this is just a convention," Professor Stephen Haseler, Professor of Government at London Guildhall University, said yesterday. "It is all part of the question of Britain not having a written constitution - you get away with what you can get away with.
"Reform of the relationship between church and state is in my view inevitable in the years to come, and who's to say what the position will be 10 years from now? The purpose of the coronation is for the King to take an oath. It is a very bizarre ceremony - at one point the monarch is surrounded by a canopy and the churchmen presiding throw oil at him. It's a so-called anointing, which is nothing more than a throwback to the belief in the divine right of kings. It's full of mumbo-jumbo. The oath will certainly change and I imagine that the question of the monarch also being Defender of the Faith will go, in favour of some multi-faith alternative."
And then, what of the woman herself? Has Camilla Parker Bowles, who destroyed her own marriage for love of the Prince, abandoned all hope of one day marrying Charles? The goalposts may keep moving. One day public acceptability may be hers.
In this context it is fascinating to observe the details that have been emerging in the last three days about the contacts between the woman who has become celebrated for staying silent about the whole affair, and the editor of the Sun newspaper, Stuart Higgins.
Mr Higgins, 39, has a long track record as a royal reporter, having provoked questions in the House about royal security in 1982 when he gained access to Highgrove, the Prince's Gloucestershire home. He was the Sun's royal correspondent before rising through the paper's hierarchy to succeed Kelvin Mackenzie as editor two years ago. He is known to have made contact with Mrs Parker Bowles and maintained it down the years. Speculation is rife in Fleet Street that it was this contact which helped the paper gain early access last week to details of the Queen's letter urging her son and daughter-in-law to divorce.
This link might be seen as a shrewd investment by Mrs Parker Bowles in a future where the Sun, with its huge influence over popular opinion, could prove a powerful ally in helping to create a sympathetic climate for the couple's public happiness.
As the royal family exchange their Christmas gifts at Sandringham this evening they will be without the Princess of Wales for the first time in more than a decade. The possibility that they may one day be gathered there welcoming a different consort for the Prince is perhaps not one that can be entirely ruled out.
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