David Cameron wants to cut immigration but he cannot just say so. This is because he is a new modern Conservative and, as I understand it, they are banned from saying anything with which Norman Tebbit could agree. So instead of immigration, the New Moderns talk about demography. This is why Dave gave a speech yesterday to begin a “grown-up conversation” on demography.

It was an unmissable event, not least because I have never heard a politician have a grown-up conversation, but he chose his subject well, for children are not that keen on demographics. Playground taunts you will never hear include, “My underlying trend is bigger than yours!” or “Don’t be such a cohort!”.

Dave was starting his conversation at something called the Ideas Space. It sounded intriguing, as if we might all be defying gravity and floating around with jetpacks, having ideas while eating weirdly coloured space food from tubes. Sadly, the Ideas Space turned out to be a room with hardly enough space for people, much less ideas.

“As Auguste Comte said,” cried the man introducing Dave, “demography is destiny.”

How grown-up was that? Auguste Comte, eh? I am sure that when he heard this Gordon Brown, the most intellectual politician in the world, was so jealous that he threw his favourite volume of Wittgenstein’s Tractatus Logico-Philosophicus across the room.

The speech was 40 minutes long and Dave was racing through it like a bat out of hell. It was, I can report, so grown-up that several people almost fell asleep. Still, it provided the following top tips for those of you who will be inspired by Dave to have your very own grown-up conversation on demography:

— Speak in numbers. Dave was not afraid to sound like the talking clock. The best numbers have decimal places, for they sound more scientific. Dave referred to “bald figures”. I had assumed all figures were bald but perhaps some have little wigs. The best figures are those that are clear, like plastic

— Throw in a bit of history to make it seem normal. Dave explained that he is following in the footsteps of William the Conqueror, who was so interested in migration and the effect of Polish plumbers that he did the Domesday Book

— Talk about atomisation. Dave says that almost everything can be blamed on “the atomisation of society”. I had visions of little electrons with ASBOs pinging around Britain, creating family breakdown and havoc. Who knows, but it sounds very grown up

— Economics are key. Drop in copious references. “It is not enough to consider broad macroeconomic effects,” said Dave, sagely. Later he added: “Life, as I’ve often said, is not just about economics.” No, I thought, because it’s about atomisation, decimal places and William the Conquerer

— Dare to be dull. Never talk about houses when you can reference “household formation”. Don’t speak of people but of population trends. Also, and this is vital, quote Richard Layard, the economist and happiness expert; if in doubt, use Wikipedia to cheat

— Use the occasional talking point. Yesterday Dave told us: “The speed of a car in rush-hour London is only half the speed of a cyclist.” It means nothing, but in an interesting way. Also, Dave told us: “An individual living alone consumes 40 per cent more water than they would if they were living with someone else.” Isn’t that odd? But then single people do not share a bathroom and so they can take more baths.

So there you go. Fewer immigrants and more atoms, slower cyclists and faster baths. Dinner parties were made for this.

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