King Charles III: could MPs turn on the Royal family after the death of the Queen?

At the heart of the play is a decision by Charles not to sign a bill that has been passed by both the House of Commons and the Lords – a move that puts him on a collision course with the prime minister and places the entire future of the Royal family in doubt. Charles sticks to his guns, claiming there is no point to the monarch if he or she cannot take a stand on a piece of legislation they find abhorrent, and there follows a series of fraught negotiations.

The prime minister tries to change Charles’s mind and keep the crisis out of the papers, while members of Charles’s family fight over the rights and wrongs of his case. A formidable Camilla (played by Margot Leicester) defends her husband to the hilt, while William (a subtle Oliver Chris) is unable to decide whether he should support his king and father or if, by doing so, he threatens the entire institution of royalty.

The Duchess of Cambridge (who would normally be styled the Princess of Wales after her husband becomes heir to the throne), meanwhile, feels no such indecision – Charles must be stopped. Played superlatively by Charlotte Riley, Kate here is a manipulator, determined on power for herself and to protect her children’s future, aware she is dismissed by the public as a “plastic princess” and underestimated by Charles, who says what she “brought to us” was “better hair” and “a sense of fashion”. Her soliloquy, addressed directly to the viewer, is shocking in its intensity.

The drama is heightened for artistic effect, of course. But the scenario it imagines is one we should take very seriously indeed. After all, we already know Charles has a more interventionist approach to policy than his mother. As Prince of Wales, he sees it as his responsibility to lobby ministers on behalf of causes he holds dear.

The government spent hundreds of thousands of pounds of public money between 2005 and 2015 resisting calls under the Freedom of Information Act to share the so-called “black spider letters” that Charles wrote to ministers, because the Attorney General felt they could undermine his “position of political neutrality”. When the letters were revealed, much of the British public were surprised to read what they saw as harmless interventions on behalf of the overfished Patagonian toothfish, heritage sites and school dinners.

But should Charles – who once said he would not be confined to a life “cutting ribbons” – have intervened at all? Critics argued that the letters revealed a propensity to interfere in the political process and represented an abuse of his position. And it has been reported that Charles is keen to make his mark quickly when he becomes king and show how his reign differs from his mother’s.

In his role as head of the Church of England, he has suggested that he wishes to be “defender of the faiths”, not “defender of the Faith”, a position that has baffled the established Church. But, in constitutional terms, what could he really do? Yes, he could make speeches about his passions and refuse to receive certain state visits. In 1999 he boycotted a banquet given by the Chinese President at China’s embassy in London, in protest at that country’s treatment of Tibet. But could he actually begin to block bills?

The last royal to refuse royal assent was Queen Anne in 1708, over a bill to arm the Scottish militia, and no monarch has dared do it since the system of constitutional monarchy we know today – whereby the prime minister and Parliament act and the monarch advises, encourages, warns and signs the bills – became effective in the 19th century.

There have, however, been standoffs between monarch and Parliament. The greatest was in the 1830s, over the Reform Act of 1832, which enfranchised men of property and granted seats in the House of Commons to large cities that had sprung up during the Industrial Revolution. Charles Grey, the Whig prime minister fighting Tory resistance to the bill, asked the king, William IV, to create Whig peers to get the bill through the House of Lords. The king refused and Lord Grey resigned. There was rioting and talk of civil war and the king was hated – even pelted with mud when he went out. In the end he relented and agreed to create the peers.

There was also a constitutional crisis in 1839, early in the reign of Queen Victoria, when her beloved Whig prime minister Lord Melbourne lost a vote in Parliament and declared his intention to resign. Victoria reluctantly asked the Tory leader Sir Robert Peel to form a government but then refused his request that she change her Whig ladies-in-waiting, whom she adored, for the wives and relatives of prominent Tories. Peel, in turn, refused to take office, but Queen Victoria’s popularity was damaged. As the diarist Charles Greville said when commenting on what was called the Bedchamber Crisis: “She has made herself the Queen of a party.”

Charles, no doubt, will be acutely aware of these historical precedents. Every time there has been a standoff between the monarch and Parliament, it has been to the detriment of the monarch’s reputation. He will also know that our Queen has become one of the most popular monarchs in history due, in part, to her careful effort to remain politically neutral. The Queen will question politicians closely, often taking the other side of a debate – Mrs Thatcher memorably complained she was “the kind of woman who could vote SDP”. But she always signs the bills.

Will Charles be able to temper his natural instinct to interfere? In the BBC drama, he makes robust arguments in favour of his position. If the monarch knows everything, has met everyone, hears the highest political arguments, then why not do something with this knowledge? Why sign off documents like a mannequin? But this staging of Bartlett’s play also makes clear the dangers of interfering. From funding the rebuilding of Windsor Castle, to Charles’s confession of adultery, to the tragedy of Diana’s death, events have occurred throughout the Queen’s reign that have threatened the future of the Royal family. It has survived and remained strong. A decision to withhold royal assent, however, may be the moment that really brings the house down – to spectacular effect.

Prof Kate Williams is a royal historian and author of Young Elizabeth. King Charles III is on BBC Two 
on Weds at 9pm