David Cameron can now feel that he has finally arrived as a statesman and man of words. Yes, opinion polls have been telling us for months that the Witney MP is well on track to become Prime Minister.

But never mind Downing Street next year, this month Mr Cameron has good cause for serious pride after making it into the new edition of the Oxford Dictionary of Quotations.

That’s the good news. For the Tory leader might wince a little when his eyes alight upon the words: “We, the people in suits, often see hoodies as aggressive, the uniform of a rebel army of gangsters. But hoodies are more defensive than offensive.”

For, of all his words of wisdom, ODQ has selected his ‘hug a hoodie’ moment, which left him facing derision in the tabloids and the wrath of those party members who still have pictures of Norman Tebbit in their committee rooms “We had to include that one,” explained the dictionary’s long-serving editor Elizabeth Knowles. For she is charged with not just bringing together the most memorable lines uttered in the English language, but the ones that have, for good or ill, stuck in our collective memories.

At least Mr Cameron will find himself joining an impressively varied intake of newcomers to this the most prestigious of quotation dictionaries.

Another modern leader, Barack Obama, is there with: “The arc of history is long but it bends towards justice,” even if he did borrow it from a Martin Luther King sermon from 1968.

But both politicians must surely find themselves in awe of the highly quotable Sarah Palin, effortlessly grabbing an ODQ place with: “What’s the difference between a hockey mom and a pitbull? Lipstick.”

ODQ readers are also treated to the wisdom of another high-profile lady who has gone through a few lippy sticks in her time, and joins contributors from the 21st century to make a mark on the language. “Dress cute wherever you go,” Paris Hilton tells us. “Life is too short to blend in.”

The grin on Ms Knowles’s face suggests that, for all her experience as a lexicographer, she identifies fully with the lovely quote from the late broadcaster and jazz musician Humphrey Lyttelton: “As we journey through life, discarding baggage along the way, we should keep an iron grip, to the very end, on the capacity for silliness. It preserves the soul from desiccation.”

The seventh edition of the ODQ includes more than 20,000 quotations from more than 3,500 authors. They range from the Chinese philosopher Lao Tzu (“A good traveller leaves no track or trace”) to Michael Fish (“A woman rang to say she heard there was a hurricane on the way”), with the seventh edition containing 150 debutants, including Oxford author Philip Pullman (“‘Thou shalt not’ might reach the head, but it takes ‘once upon a time’ to reach the heart”).

This time it has meant a few big names have had to go. Even before the break-up of Oasis, Mrs Knowles had decided Noel Gallagher no longer merited a place between Galileo and the novelist John Galsworthy.

Pity really, I quite liked Noel’s “I would hope we mean more to people than putting money in a church basket and saying ten Hail Marys on a Sunday. Has God played Knebworth recently?” if only to prove how much Oasis borrowed from John Lennon and the Beatles.

But editing the dictionary is a ruthless business, particularly this time around.

“Previously it was possible to expand the book to include new material without too great a necessity on cutting back on what was already there,” she observed. “However, after nearly 70 years, the dictionary had reached the point at which length could be a problem.”

Ms Knowles, who also edited the fifth and sixth editions, believes she has always been helped by clear pointers from its earliest days in making her choices, with one clear guideline to include what is being quoted, rather than what is quotable.

The easiest cuts, she says are the quotations, topical at the time, but which have faded from sight. An example of a quote that burned only briefly came on the tenth anniversary of the death of Diana Princess of Wales, when her younger son said: “To us, just two loving children, she was quite simply the best mother in the world.”

Since that date, however, it has barely been used, so has been left out.

Every item in the database that Ms Knowles has lovingly built up — created by combing daily through the print and broadcast media, books, journals and the Internet — has to be carefully researched for its authenticity. The team is now greatly helped by search engines to establish the popularity and usage of quotes, as well as by letters and suggestions from readers.

“The more recent a remark is, the more difficult it is to predict whether or not it has lasting qualities and at times it is necessary to make a judgment call,” she observes. “With a book like this, I think the important thing is that it is the place you go to when you want an answer to the question, ‘who said that?’ So, to some extent, you are always trying to second guess the readers.”

So, it means always having a bubbling-under category, that could make it if the quotes stand the test of time. Fingers crossed then for Pete Doherty on prison life (“A lot of gangsters and Radio 4”) and Boris Johnson on the Olympics (“I say to the Chinese, and I say to the world, ping-pong is coming home”).

With its 70th anniversary fast approaching (it will have been and gone by the time the next edition appears), Ms Knowles, who lives in Witney, provides a six-page history of the ODQ in the new edition. While it does not quite rival the story of the Oxford English Dictionary, which featured such a strange collection of heroic, obsessive and crazed figures, it nevertheless makes for fascinating reading.

The idea of an Oxford Dictionary of Quotations was first mooted as early as 1915, with the idea that this would be limited to poetry and “not foreign quotations”. But the idea was not to be followed up until the 1930s, when the principle of A-Z author organisation was established.

It was also clearly aimed at a highly educated readership, with the first dictionary to include quotations from major writers likely to be quoted by the most literate and cultured. The first edition did not appear until October 1941, two years after the outbreak of the Second World War, with readers assured in the introduction that; “Quotation brings to many people one of the intensest joys of living.”

Remarkably, given the date of its publication, the first edition includes only a single quote from Sir Winston Churchill, dating from 1906 and hardly one of his most unforgettable utterances (“It cannot in the opinion of His Majesty’s Government be classified as slavery in the extreme acceptance of the word without some risk of terminological inexactitude”). The great war leader was, in fact, easily out numbered by the quotes from his father Randolph. Neville Chamberlain was also absent, with no place even for his words on returning from Munich in 1938 (“I believe it is peace for our time”).

The first printing of 20,000 was exhausted about a month after publication. But trouble quickly came in the form of Lord Alfred Douglas, the poet best known for being Oscar Wilde’s lover. The famously litigious Lord Alfred was furious that he was represented by two lines — “The placid pug that paces in the park” along with “And duty is the lobster’s chief obsession” — taken from his early nonsense verse.

After lengthy correspondence, Lord Alfred later sulkily admitted that his solicitors had advised that while the publication of the disputed lines was “undoubtedly malicious and insulting”, it was not actually libellous and it would, therefore, not be worthwhile to take action for infringement of copyright. In later editions the pug and the lobster were quietly dropped. Today Lord Alfred is represented by the line: “I am the love that dare not speak its name.”

“Intelligent elasticity” was the essential editorial quality identified by Kennent Sisam, the secretary to the delegates of the OUP between 1942 and 1948. And Mrs Knowles says she is always conscious of building on the work of earlier editors.

Her own connections with the OUP have stretched over many years.

She spent ten years on the New Shorter Oxford English Dictionary and her other editorial credits include the Little Oxford Dictionary of Proverbs; Oxford Dictionary of Phrase, Saying and Quotation; and What They Didn’t Say: A Book of Misquotations.

Although she officially retired from the OUP staff two years ago, her work on the next edition is well under way. Its date is unscheduled but it is unlikely to appear for at least five years.

So, after taking us from Aberland (“For we do not easily expect evil of those whom we most love”) to Zola (“One forges one’s style on the terrible anvil of daily deadlines”) did she have her own favourite quote?

The woman behind the world’s leading quotations database pauses, as if she had never been asked the question countless times, allowing me to imagine 20,000 quotes running through her brain.

“Well I’ve always quite liked a quotation from Jawaharlal Nehru from a press conference in 1958 — ‘I may lose many things including my temper, but I do not lose my nerve’.”