Early moves are afoot to let women smash their way through one of the last remaining barriers to sex equality in Britain by giving them equal rights to the throne.
But at the first whiff of what, in constitutional terms, would be a drastic reform, die-hard hereditary members of the House of Lords tried to prevent it from even being debated.
Leading a campaign to end the ancient custom of primogeniture, by which a younger male child of a sovereign automatically enjoys rights to the throne over his elder sister, is millionaire Lord Jeffrey Archer, perhaps better known for his bestselling thrillers.
Lord Archer, whose title is not hereditary, says it is "only right in this day and age" that the eldest daughter of a sovereign should "enjoy precedence over a younger male child."
But this week when he introduced a Succession to the Throne Bill aimed at removing sex discrimination from Britain's royal line of succession, an array of peers lined up against the measure.
For the first time in the British upper chamber's 600-year history, opponents of the move forced a vote on whether the queen should be asked for permission to allow a bill to proceed. Every bill ever introduced in the House of Lords, prior to Lord Archer's, has proceeded to debate without opposition.
While the House voted 74 to 53 to allow it to be introduced, hereditary peers of all main parties are promising to fight it when it comes up for debate early next year.
Queen Elizabeth II did not have to worry about primogeniture. Her first-born was Prince Charles, so he automatically became heir to the throne.
The Queen's father, King George VI, had no problems either. He had no sons, so Elizabeth, the elder of his two daughters, succeeded him.
But what Lord Archer is worried about is the possibility that when Prince William, next in line to the throne after his father, Charles, eventually marries, his first child will be a girl and his second a boy. Under primogeniture, the boy would leapfrog onto the throne over his sister's head.
Lord Archer argues that it would be "farcical" if Prince William's first-born was a daughter and could not become queen. Nobody knows for sure, but it has been widely reported that Queen Elizabeth is sympathetic to Lord Archer's bill.
At a conference of members of the royal family held earlier this year to consider modernizing the monarchy, abolishing primogeniture was discussed.
For peers of the realm, whose titles are handed down from generation to generation, however, Lord Archer's ideas look like the thin end of a decidedly dangerous wedge. The rub is that primogeniture applies to the children of peers as well as to those of royals. If it is abolished for the monarchy, they reason, it could eventually be abolished for Britain's nobles. In addition, many peers are concerned that the hereditary principle as a whole will be heavily undermined by changing such a longstanding practice as primogeniture, and may even be abandoned altogether. Adding to the weight of such concerns, the opposition Labour Party has pledged to curb the voting rights of hereditary peers if it wins next year's general election.
So when Lord Archer asked the House for permission to make a "Humble Address" to the queen so that his bill could be debated, usually a mere formality, dozens of peers objected by shouting the ancient formulation "not content." Lord Chancellor Mackay, the head of Britain's legal system, who acts as Speaker of the upper house, had to call an unprecedented vote on a Humble Address.
Not all British aristocrats are keen on primogeniture. Baron Gainsford, a hereditary Conservative member of the House of Lords, says: "I have only daughters, so my younger brother is in line to my title. But I would love it to go to my eldest daughter."
It will be several years before Prince William marries, but early passage of Lord Archer's bill would have an immediate impact on the queen's family. Elizabeth's daughter Princess Anne, her second child, would automatically move ahead of her younger brothers, Prince Andrew and Prince Edward, in the line of succession.