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Labour's Jeremy Corbyn is not the first party leader to miss a Privy Council meeting, Cameron has too Getty

Jeremy Corbyn's patriotic credentials are under scrutiny once again after the Labour leader's team said he had "prior commitments" that would prevent him from being sworn into the Queen's Privy Council. The move means that the life-long republican will not have to bow before the monarch after joining the Queen's 600-strong group of formal advisers.

The ancient ceremony is just one of the many rituals the leader of Her Majesty's opposition is expected to undertake. Another seems to be singing the national anthem during Battle of Britain commemoration services at St Paul's cathedral – an act Corbyn failed to fulfil and subsequently received a lot of flak for. However, the Privy Council controversy is less clear cut.

The elite organisation, which draws its membership from the clergy, the judiciary, royalty, the House of Commons and the House of Lords, holds monthly meetings typically at Buckingham Palace and Windsor Castle. Beyond advising the Queen, the councillors are crucially given access to briefings from the security services. In exchange, the establishment figures are expected to make a vow of secrecy in a convention established in 1250 under Henry III.

"You will in all things to be moved, treated and debated in council, faithfully and truly declare your mind and opinion, according to your heart and conscience; and will keep secret all matters committed and revealed unto you, or that shall be treated of secretly in council," the oath reads.

But it is important to note that members of the Privy Council do not have to be sworn into the group straight away. It took David Cameron three months to bow before the Queen in March 2006 after winning the Conservatives' leadership election. Likewise, it took just under two months for Nick Clegg to be sworn into the Privy Council in 2008, and the former deputy prime minister was later accused of "snubbing" the monarch in 2013 for failing to attend four meetings of the organisation. His aides explained that he also had prior commitments.

So when Alan Duncan, a Tory MP and privy councillor, accused Corbyn of "putting his politics above the Queen" in an interview with BBC Radio 4 Today's programme on 8 October, the same accusations must be levied at his own boss Cameron and his former coalition government colleague Clegg.