THE trouble with history, as Arnold Toynbee noted, is that it’s just one damned thing after the other. And the trouble with writing contemporary history is that it can easily be overtaken by events.

Iain Martin’s highly readable and well-informed survey of the scandals and triumphs of the City of London since the deregulation Big Bang of 1986 was hit by an even bigger bang just as it reached the bookstands: Brexit.

Martin is a self-confessed free marketeer who obviously loves the culture of the City, even though he is critical of the greed and recklessness of the investment banking fraternity. His objective was to demonstrate that the City of London had largely weathered the 2008-12 crash and, on the 30th anniversary of the eponymous bang, was going from strength to strength.

And so it was. In 2013, the UK managed 78 per cent of all EU foreign exchange trading; 85 per cent of hedge fund assets; 50 per cent cent of Europe’s fund management. Financial services account for 2.1 million jobs (100,000 in Scotland) and £65 billion in taxes. Highly leveraged banks like Northern Rock and RBS may have come a cropper in the crash, but deleveraging and the new financial regulations since then actually created a renewed demand for the City’s unique financial skills. Then came the EU referendum.

The paradox of the City’s success in recent years, as Martin explains, is that it has ridden on the back of a currency that Britain refused to adopt: the euro. The introduction of the single currency in 2001 generated a market worth trillions of euros to be managed, traded, hedged and securitised. Thanks to the “passport” for financial services, any bank in the single market could be a centre for trading euros. The City became, as Martin put it, the “crossroads between the dollar and the euro”.

But not, perhaps, for much longer. If the UK fails to negotiate a new passport to handle the euro trade, then it could be curtains for the City. Other centres in the eurozone itself, like Frankfurt, would dearly like this business for themselves.

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The European Central Bank, based in Frankfurt, has long argued that financial institutions handling billions of transactions in euros should be in the eurozone, not just the wider EU. Now Britain is out of the European Union altogether, the pressure to lock the City out of eurozone trade may become irresistible.

Of course, the clever people in the City of London might continue to use their skills in the wider global financial marketplace. Eurosceptics like Martin argue that the era of big trading blocs like the EU is over. Britain could be better off managing the rest of the world’s money rather than just Europe’s. After all, Wall Street, whose culture and practices have been emulated by the City for the last 30 years, still turns a dollar or two.

But it may equally be that the era of financial capitalism, of which the City of London is the global star, might also be on the wane. As a cheerleader for the City, this is a possibility that Martin does not wish to consider, though he is not afraid to point to the City’s moral failings. He condemns the rapacious, post-Big Bang culture in which “corporate larceny was discussed as though it was evidence of dynamism”. But Martin insists that the City of London, is “a great British success story” despite the big bonuses that have made it synonymous with greed.

However, it may not be the champagne lifestyle that destroys financial capitalism, but the fact that it has ceased to be capitalism. When banks became too big to fail, they became, as Martin puts it, “wards of the state”, insulated from the creative destruction that is the essence of the free market system.

They became dependent on taxpayers’ money, £1 trillion of which had to be mobilised to bail out the banks after the 2008 crash, according to Mervyn King, the former Governor of the Bank of England.

A welfare state for banks wasn’t quite what Margaret Thatcher had in mind when she threw the City open to competition in 1986.

If Brexit causes another financial crisis, taxpayers may this time tell bankers: stand on your own two feet.

Crash Bang Wallop: The Inside Story of London’s Big Bang, by Iain Martin is published by Sceptre, priced £25