By Rosie Dawson
Producer, BBC Radio 4
Not many people outside Parliament become right honourables and it's what I wanted more than anything
Michael Portillo, ex-cabinet minister
The Privy Council is one of Britain's oldest institutions, dating back to the earliest days of the monarchy and made up of those chosen by the King or Queen to advise them in important matters of state.
Elizabeth I's Privy Council had about 40 members. Today there are 546 - appointed for life by the Queen on the prime minister's advice.
Senior members of the Royal Family are on it, as are the archbishops of Canterbury and York.
But anyone aspiring to become a privy counsellor should seek it through a career in politics rather than matrimony or the cloth.
Most privy counsellors are, or have been, members of Parliament. It is the Privy Council that puts the "right" into "right honourable" and membership is highly prized, according to former Defence Secretary Michael Portillo.
"Right Hon is a title we covet very much indeed", he says, "partly because no one outside Parliament knows what it means. They tend to think all MPs are right honourables but they are not - it's only those who are admitted to the Privy Council.
"Not many people outside Parliament become right honourables and it's what I wanted more than anything."
New members of the Privy Council are sworn in at a ceremony at Buckingham Palace.
Clare Short was not happy about curtseying to the Queen
"We had a rehearsal to become members," former International Development Secretary Clare Short recalls.
"There was a big thing for my generation about what to do, because women used to curtsey and I'm a sixties kid. I can't be curtseying."
In these days of constitutional monarchy, the Privy Council no longer advises the monarch.
Today only a handful of members attend the monthly meetings and their business is simply to seek the Queen's formal approval to a number of orders which have already been discussed and approved by ministers.
Most deal with matters which Parliament has delegated to the executive, as various as the closure of burial grounds, the proclamation of a new coinage and the dates of bank holidays.
However, others are founded on something called the Royal Prerogative, discretionary powers left in the hands of the Crown but exercised by ministers.
These prerogative powers can be used to create primary legislation and do not have to pass through Parliament.
Patrick O'Connor QC, author of a recent report on the Privy Council, believes such powers are potentially open to abuse.
'Light of day'
"In relation to prerogative powers this is a route to evade scrutiny in Parliament," he says. "Primary laws that affect people's lives are created and never see light of day in Parliament."
He cites the banning of trade union membership at GCHQ under Mrs Thatcher, the Blair government's decision to allow its advisers to issue direct instructions to civil servants, and the eviction of the Chagos islanders from their homeland in the late 1960s as examples of the mis-use of these prerogative powers.
Justice Secretary Jack Straw says his forthcoming bill on the governance of Britain will remove many of the remaining prerogative powers "where they matter."
"We're moving the power to make foreign treaties from the prerogative to Parliament, and we are proposing to bring the civil service under statutory control."
But while the prerogative powers may be withering on the vine, it seems the Privy Council will survive for now.
In spite of occasional calls for its abolition from within the judiciary, most politicians appear to regard it with affection as a harmless relic of our constitution, a throwback to a bygone age.
What's the Point of the Privy Council can be heard on the BBC Radio 4 iPlayer, which is linked to in the top right hand corner of this page.