For once, global stock exchanges are the story – not the shares traded on them. But the extraordinary wave of proposed mergers presents questions for policy makers. Competition has already been increased and regulation tightened. Regulators should scrutinise the form these new exchanges take. But they should manage – not resist – the force of the market.

Stock exchanges are built in the image of the markets they serve. Once every city had a bourse. Now that capital is global, consolidation is being applied on an international scale. The idea that exchanges must be national entities is no longer true. Those in the US who object to Germany’s Deutsche B?rse running NYSE Euronext should remember that NYSE owns the Paris exchange.

The real concern that mergers raise is the threat that a larger provider abuses its dominance. In the past decade, US and European regulators broke exchanges’ trading monopolies. The ensuing fragmentation has worked well for share trading. In the UK, the London Stock Exchange now handles less than 60 per cent of trading in the FTSE 100. The rest is dealt on smaller platforms, in “dark pools” and through facilities offered by banks and brokers.