The battle for ownership of the London Stock Exchange (LSE) has hotted up again with the announcement that an Australian investment bank, Macquarie, is thinking about a bid. So far, it has only been other stock exchanges expressing an interest in London's exchange and it comes as a surprise that an investment bank should enter the fray.

But Macquarie has a reputation for acquiring monopoly businesses that offer fat margins, although none of its acquisitions so far have run to national stock exchanges.

The contest for the LSE has already prompted a high-profile row between its owners and potential acquirers. Deutsche Börse lost its chief executive in the wake of one dispute, but it is still thought possible that the German exchange will come back with another bid. Euronext, the owners of the Dutch and French stock exchanges, is widely spoken of as the most likely successful bidder.

Deal activity - anything related to mergers or acquisitions (M&A) - has picked up markedly in recent months, particularly in the UK.

Reports of takeovers - real and imagined - hit the headlines on a daily basis. The latest story to emerge suggests that Britain's third largest mobile phone operator, O2, was about to be bid for by a consortium consisting of German and Dutch operators Deutsche Telekom and KPN. The deal has broken down because of "differences" between the erstwhile partners.

Deal activity correleates with the economic cycle. Not surprisingly, therefore, we see some of the most cyclical businesses of all - mining companies - involved in all sorts of M&A activity.

BHP Billiton is a UK-listed company that is best thought of as either an Australian or, perhaps, global operator that recently gobbled WMC - also of Australia. The share price of Xstrata rose early this week, helping to boost the FTSE 100, on news that it is buying part of Canadian company Falconbridge. Xstrata is based in Switzerland, listed in the UK and largely digs copper out of Australian mines. There are quite a few companies with UK listings that have little connection with the UK economy. Benefits include greater transparency for investors and, hence, a better share price.

UK pension funds and other investors who like to track UK-based share indices find themselves owners of assets like Antofagasta, another mining company, not Australian but Chilean.

One of the interesting aspects of all of this is how genuinely global is the London Stock Exchange. One way or another, many of the companies listed in London have activities - and owners - that increasingly reflect globalisation. Does the banking giant HSBC have a nationality or is it simply a genuinely global identity? Shell, always described as the "Anglo-Dutch oil giant" recently consolidated its listing structure in London and, combined with BP, now makes up almost 20 per cent of the FTSE 100. BP might have "British" in its name but, like Shell, could also be thought of as a truly global company.

One of the reasons why all of this has happened, and why the UK has so many large global businesses, is that nobody makes a fuss when a foreigner comes in and buys a British business.

For all of the furore about the LSE, there has been very little nationalistic nonsense about losing a British champion to Johnny Foreigner. Nobody gets very excited when British companies evolve into global identities.

Indeed, the City of London itself has long ceased to be a very British entity, with foreign financial institutions now dominating all aspects of business here. It's this relaxed attitude to ownership and control that makes London an attractive place for so many foreigners.

Earlier in the summer there was consternation and alarm in France prompted by rumours that Pepsi was going to bid for Danone. Politicians fell over themselves to denounce the mere idea with both the prime minister and the president getting in on the act. The contrast with UK attitudes couldn't be starker.

Sometimes we hear moans about the Wimbledon phenomenon: the presence of world-class businesses in London but with little connection to Britain. But mostly we recognise that London's success as financial centre owes a lot to questions about nationality never being asked.