I was pleased to read recently week that Morgan Sindall, the British civil engineering company that has carried out the lion’s share of work on London’s Crossrail scheme, is once again thriving and in the market for new business. This is good news not only for the firm’s 5,700 highly-skilled employees, but for shareholders and, just as important, the UK.

But it does rather highlight the fact that Crossrail looks as if it could be one of the last major construction projects that is British-funded, British-designed and carried out, for the greater part, by British workers. If John McDonnell, the shadow chancellor, is to be believed – admittedly not the default position at Reaction – potential UK investors are withholding as much as £700 billion from essential infrastructure improvements, preferring to invest it in the capital markets or pay it out as dividends. Instead, it is foreigners who will take the risks and reap the rewards.

Don’t get me wrong. Investors rarely throw good money at bad projects or rogue economies. And once in, unlike their British counterparts, it is usually for the long term. When BMW, Tata and Nissan essentially bought out the British car industry, there were fears in some quarters that production would gradually leach back to the home countries or be relocated to, say, Mexico or India. Such fears proved unfounded – though, post-Brexit, there will be testing times to come.

And yet and yet … When a country reaches a certain tipping point, beyond which it assumes that foreign investors are the answer to any large-scale funding problem, alarm bells should sound.

The irony of Brexit as an attempt to regain sovereignty should not be lost as more and more of our manufacturing companies answer to foreign governments and foreign boardrooms. But, largely unnoticed, construction is following suit. Not only do we not build anymore (with almost as many East Europeans as Brits employed on sites), we don’t even fund what others build. Instead, we rely increasingly on the expertise of the City of London to keep us solvent, not realising perhaps that one of the City’s more rewarding tasks these days is the brokerage of inward investment.

We may think we have been uniquely clever, presiding over an economy in which others not only prime the pump but built the pump in the first place. But a reckoning is coming. A country that leaves the heavy lifting to others may avoid immediate back pain, but over time it is bound to be weakened, its muscles atrophied from lack of use.

We risk ending up like the Eloi at the far end of the cycle in H.G.Wells’s Time Machine, so far evolved that we barely have the strength to get out of bed. Which begs the question, who will the Morlocks be?

The Chinese are bursting to design, fund and build HS2, the high-speed rail link from London to Birmingham, Manchester and Leeds. Chinese money is also behind the stalled Hinkley Point nuclear power station, which, should it ever receive government approval, will, of course, be built by the French.

It is true that Beijing is not currently flavour of the month in Downing Street, where Theresa May is understood to have removed President Xi Jinping from her 2016 Christmas card list. But the Asian giant is dangling some hundred billion pounds-worth of investment in Britain and is unlikely to drop out of the picture in any significant way. Even if it does, money for all our highest-profile construction projects, from London to Leeds, will have to come from somewhere – most obviously the Gulf – because it certainly won’t come from UK investors.

With rare exceptions, British investors would rather spend their fortunes on ocean-going yachts, private jets, New York condos and villas in Monte Carlo than risk it on major projects. They place their cash in hedge funds and offshore accounts, not factories or roads and railways, which they consider just soooo last century. Needless to say, few of them live here.

Consider the following:

• A group of wealthy Far Eastern investors is planning a major spending spree in Birmingham – and have huge regeneration schemes in their sights. A consortium headed up by Denise Li, president of GlobalChina Wealth Management, plans to filter capital from the super-rich of China and Taiwan into property, infrastructure and energy schemes in the UK.

• The UK government has approached Abu Dhabi sovereign wealth funds seeking investment in major infrastructure projects. The chief executive of the UK Trade and Investment Corporation met with leading investors from the United Arab Emirates to try to drum up investment in projects including the high-speed rail project HS2, and the UK government’s Northern Powerhouse initiative. Offering the chance to get involved in “the biggest programme of railway building in the United Kingdom since the time of Queen Victoria”, the head of the British delegation said the Government would “love to see sovereign wealth fund money” invested in HS2, and in efforts to build new infrastructure in Manchester, Birmingham, Sheffield and Leeds.”

• Gulf family businesses and private investors are heavily involved in London real estate. Investors from the UAE accounted for more than 20 percent of buy-to-let property sales in the UK in 2015.

According to the Office for National Statistics foreign direct investment in the United Kingdom increased by ÂŁ38.4bn in the first quarter of 2016. By comparison, inward investment into Germany for the whole of 2015 was ÂŁ5.3bn. The Germans, while never likely to reject a mutually-beneficial deal, are careful to maintain sovereignty over their economy. They also like to build their own roads and railways.

Big projects must be funded. Investments have to be made. And we should not assume that all gift horses follow the Trojan model. But the risk today is that the situation is moving out of control. Inward investments are shaping up to be like those reverse mortgages we have all been warned about. Sovereign wealth funds and mega-corporations are not charities. In the long run, they are in business to make a profit, and it will be our children and grandchildren who ensure that they do. In the meantime, the governments and big corporations of China, the Gulf states, India, Japan, Taiwan, Russia, France and Germany have become the key movers and shakers of the British economy, making most of the employment and strategic decisions that matter. No wonder the bulk of top-end real estate in London is owned by foreigners. It’s THEIR country after all – in both senses of the word, THEIR capital.