What goes up must come down. And the higher you climb, the further you fall.
You could apply both these maxims to London property, and get an accurate reflection of the market mood right now.
London prices have spiralled since the financial crisis, thanks to cheap finance and the world's freebooting super-rich, who want a safe home for their wealth.
When blighted Deptford is being touted to Hong Kong investors as a shiny new investment opportunity, we have surely hit peak London.
Hedge Your Bets
Hedge fund managers certainly think so. Reports suggest they are frantically shorting the shares of emblematic London estate agents Foxtons and Savills, and housebuilder Berkeley Group.
They think London has risen too far too fast, and now it's crunch time. It isn't hard to see why.
London prices have leapt almost 50% from their trough in the second quarter of 2009, against just 19% nationally, according to Halifax.
Prices in the capital are now 10% above their pre-crisis peak, which everybody thought was unsustainable at the time.
Across the rest of the UK, they are still 6% lower than in 2007.
There are already signs of a slowdown in the capital. The average price of a central London flat fell 9% last year, according to Home.co.uk, while the number of flats for sale rose 64%.
Online estate agent Emoov says London demand fell 28% last year, as over-stretched buyers moved out the capital.
The rot is starting at the top of the market. Westminster, which has the highest average property prices in the country at £1.7 million, saw the biggest decline in demand at 42%.
With Chancellor George Osborne's stamp duty reforms hitting those paying £932,000 or more, high-end London is losing its charm.
Only Bexley is booming now.
Wealthy buyers also nervous about the prospect of a Labour victory in May's general election, because they don't fancy paying Ed Miliband's mansion tax.
George Osborne has already hit cash-rich foreign owners with capital tax gains when they sell their UK property. Many are now looking for a cheaper, safer haven for their money.
Crash Bang Wallop
The Centre for Economics and Business Research expects London property to fall 3.3% this year.
If London is buckling even with today's all-time low mortgage rates, things could turn nasty when borrowing costs finally rise.
Many would welcome a crash, especially young Londoners who see no other way of getting on the property ladder.
Analysts have repeatedly called the London property crash, of course, and been repeatedly wrong.
But they only have to be right once.
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