英国在于2016年6月24日举行的全民公投中决定退出欧盟，此举令全球股票市场当天的损失超过2万亿美元。这是历史上单日绝对价值损失最高的一天，随之而来的还有对英国经济发展前景的悲观情绪。

但在对于即将到来的英国“脱欧”的种种担忧中，还存在一个好消息，那就是“脱欧”可以令英国经济远离疲弱、负债累累的其他欧盟国家的拖累（这些国家合称PIIGS，即葡萄牙、爱尔兰、意大利、希腊和西班牙）。同时，英国还有机会将重心放在发展与中国等发展较快经济体的关系上。英国首相特蕾莎·梅在今年1月曾表示，“随着英国脱离欧盟，成为更加外向型经济体”，英国“将深化发展英中关系的黄金期……我们致力于建立广泛深化的伙伴关系，共同努力应对全球挑战”。

这其中，一个格外令人振奋的消息就是将于年内开通的“沪伦通”——上海证券交易所与伦敦股票交易市场的互联互通。“沪伦通”或将极大促进中英两国之间的投资机会。英国和中国政府都承诺，致力于在2018年年底之前完成“沪伦通”的建立。这是继2014年11月推出“沪港通”和2016年12月推出“深港通”之后的又一举措。

虽然中国一直在逐步降低跨境资本流动的限制，但在该领域依然存在相当大的壁垒。股票交易市场互联互通计划可以令离岸市场投资者相较以前更自由地进入中国市场。有证据显示，虽然初始规模较小，但“沪港通”带来的双向投资流动极大降低了两个市场间的价差。很多中国企业同时在上海和香港证券交易所上市，但（在把以不同币种计价的差异包括进去之后）两个市场存在巨大价差，虽然它们代表的是完全相同的营收。资金在两个市场间更自由的流动最终将抹平溢价，因为投资者会抓住机会，在价格更高的市场卖出，在价格相对较低的市场买进。虽然“沪港通”开通之后，上交所A股相对于香港H股依然存在溢价，但平均溢价在2018年5月中旬已经降到了20%左右，这与过去动辄高达100%的溢价相比已经相当平缓了。

根据“沪伦通”计划，英国投资者将能够搭上中国发展新机会的快车，同时中国内地投资者也可以更好地在亚洲以外的区域令其投资多样化。已经投入使用的“沪港通”和“深港通”给投资者带来的多样化选择相对有限，因为这些股票交易市场间具有不可避免的相互依赖性，从理论上来说沪港深每个市场都是同一个国家的一部分。

促成“沪伦通”计划成型的一个主要动因是伦敦已经成为中国官方货币人民币的重要交易中心。伦敦是除香港外最重要的人民币离岸交易中心，并于2016年在人民币清算量上取代新加坡成为全球第一。此外，伦敦市场在以人民币计价的债券发行量上也一直遥遥领先。例如，2016年伦敦股票交易市场上以人民币计价的债券多达95种，价值总量约近60亿美元。2018年1月的SWIFT人民币追踪报告显示，2017年伦敦是大中华区以外全球最大的人民币清算中心。此外，“沪伦通”还可以利用欧洲其他国家对中国日益增长的关注——如2015年11月德意志交易所集团与上海证券交易所和中国金融期货交易所在法兰克福联合推出了中欧国际交易所。正如“沪港通”取道香港为海外投资者进入中国内地市场提供机遇一样，新的“沪伦通”将为欧洲投资者进入中国提供更多机会。

但这并不意味着新成立的“沪伦通”不会面临严峻挑战。或许最明显的一点就是伦敦和上海之间8个小时的时差。但这个问题可以通过在两个市场发行特别设计的金融工具得到规避。这些被称为“存托凭证”（depository receipts）的金融工具是可在一国国内市场自由交易的外国公司有价证券的可转让凭证。在“沪伦通”机制下，在伦敦股票交易市场挂牌的股票存托凭证可以在上海证券交易所交易，而在上海证券交易所挂牌的股票存托凭证可以在伦敦市场交易。此外，在伦敦股票市场交易的中国存托凭证与其他在伦敦市场交易的证券享有同样的结算条件。该“结算”是指一笔交易的执行与资金从买家流动到卖家之间的延迟。由于上海证券交易所与伦敦有着一天的时差，横跨两个市场的不同结算条件将带来很多问题。“沪伦通”于2017年推出试点项目后直到2018年才有望正式实施，也是为了彻底解决这些机制性问题。现在还不清楚的是，中国的存托凭证是否可以完全转换成上交所的基础证券。2018年5月，《中国证券报》援引申万宏源证券分析师林瑾的话说，在“沪伦通”最初设计的机制架构中，完全转换似乎并不现实，但也并不排除未来可以实现完全转换的可能性。

为“沪伦通”打下基础的一个重要里程碑是中国国务院于2018年3月31日批准了中国证监会提交的存托凭证试点计划。有趣的是，该计划同时也可用于吸引那些已经在美国上市的中国公司回到上海上市。指导原则规定，已经在海外上市的创新企业市场价值至少要达到2000亿元人民币（约合320亿美元），而对于尚未在海外上市的创新企业，如果这些企业符合最低营收和利润水平等其他标准也可被视为达标。目前在纽约上市的阿里巴巴和百度符合该标准。就在计划获批后不久的2018年4月，中国人民银行行长易纲不仅确认了新的“沪伦通”将于年底前推出，同时宣布大幅扩大现行的“沪港通”和“深港通”规模。事实上，截至2018年5月1日，“沪港通”和“深港通”的每日配额已经翻了四番，两者的新配额分别达到了520亿元人民币和420亿元人民币。虽然“沪伦通”的具体配额还未出台，但现行“沪港通”和“深港通”规模的急速扩张至少表明中国政府已经愿意允许资金进行更大规模地流动。

但对于“沪伦通”的前景，并非所有人都抱持着乐观心态。例如，咨询公司Capital Economics就嘲讽该计划“炒作大于实质”。妄下这种论断或许为时尚早，因为除非“沪伦通”真正推出，否则很难看到任何实质内容。但是，要想在中国和英国之间建立起有意义的资金流动的确需要花很长一段时间。目前，通过“沪港通”流动的资金量几乎从未达到过计划最初设定的相对较低的初始配额，因此“沪伦通”在短期内的影响似乎也可能相当有限。

但同时，我们也不应低估其长期影响力。这是中国加速自身与世界金融市场融合迈出的里程碑式的一步。为了避免重蹈低估这种重大措施影响的覆辙，我们只需回想一下亨利·基辛格在理查德·尼克松于1972年对中国进行历史性访问时说过的话：“（中美之间）双边贸易即使发展到极致，对我们的经济来说也是微乎其微的。”他现在应该恨不得收回这个论断。

The United Kingdom is less than two years removed from the Brexit referendum result that triggered a more than 2 trillion-dollar loss in global equity markets on June 24, 2016. This was the largest single-day loss in absolute value in history and it was accompanied by much doom and gloom over the prospects for the U.K. economy.

One factor balancing ongoing concerns over the pending exit from the EU is that this also involves distancing the U.K. economy from the weaker, debt ridden EU countries collectively known as PIIGS (Portugal, Ireland, Italy, Greece and Spain.) Meanwhile, there is the opportunity to focus on establishing new ties with faster growing parts of the world like China. Prime Minister Theresa May expressed in January 2018 that the U.K. "will intensify the golden era of UK-China relations... as the U.K. leaves the EU and becomes ever more outward-looking, we are committed to delivering broad and deep partnerships and working together to tackle global challenges."

A particularly exciting development is the pending link up between the London and Shanghai stock markets that promises to greatly enhance investment opportunities between them. The British and Chinese authorities have both committed to establishing the Shanghai-London Stock Connect before the end of 2018. It follows in the footsteps of the Shanghai-Hong Kong Stock Connect that was enacted in November 2014 and the Shenzhen-Hong Kong Stock Connect of December 2016.

Notwithstanding gradual reductions in the impediments to capital flows in and out of China, substantial barriers remain. The Stock Connect schemes allow investors in the respective offshore markets much freer access than before. In the case of the Shanghai-Hong Kong Stock Connect there is some evidence that, despite its initial relatively small scale, the new northbound and southbound investment flows significantly impacted the price differentials across the two markets. Many Chinese companies have shares that trade in both Shanghai and Hong Kong, but at substantially different prices (after accounting for the different currencies involved) even though they represent claims on exactly the same set of earnings. Freer movement of funds between the two markets should allow such price discrepancies to be reduced as investors take advantage of the opportunity to sell in the relatively more expensive market and buy in the relatively cheaper market. Although A-shares in Shanghai continued to trade at a premium to H-shares in Hong Kong after the launch of the Shanghai-Hong Kong Stock Connect, the average premium of around 20% in mid-May 2018 looked rather mild compared to extremes that reached above 100% in the past.

Under the Shanghai-London Stock Connect, U.K. investors would be able to take advantage of new opportunities in China just as mainland Chinese investors would more easily be able to diversify outside of Asia. The diversification opportunities offered by the existing Shanghai-Hong Kong and Shenzhen-Hong Kong Stock Connects remain more limited given the inevitable interdependence between these markets, each of which is technically part of the same country.

A major spur for the new Stock Connect lies in the fact that the city had already become a major hub for trading in China's currency, the renminbi. London is the most important external renminbi center other than Hong Kong, having overtaken Singapore in renminbi clearing volumes in 2016. The London market has also been home to significant volumes of bond issues denominated in the Chinese currency. There were more than 95 renminbi-denominated bond issues listed on the London Stock Exchange in 2016, for example, accounting for an aggregate total equivalent to approximately six billion U.S. dollars. SWIFT's January 2018 RMB Tracker confirmed that London remained the largest clearing center outside of Greater China in 2017. There is also the opportunity for the Shanghai-London Stock Connect to tap into the growing China focus evident elsewhere in Europe, as with the November 2015 launch of Frankfurt's China Europe International Exchange as a joint venture between the Shanghai Stock Exchange, Deutsche Börse and China Financial Futures Exchange. Just as the Shanghai-Hong Kong Stock Connect offered overseas investors access to the mainland China market via Hong Kong, the new Shanghai-London Stock Connect will make China access more readily available to other European investors.

This is not to say that the new Stock Connect does not face substantial challenges. Perhaps the most obvious concerns the eight-hour time difference between London and Shanghai. This problem can, however, be circumvented by the use of specially constructed financial instruments that will be issued in each market. These instruments, known as “depository receipts,” involve claims on foreign shares that can be freely traded on the domestic market. Under the Shanghai-London Stock Connect, depository receipts of London-listed stocks would be traded on the Shanghai market and depository receipts of Shanghai-listed companies would be traded on the London market. Moreover, Chinese depository receipts traded on the London market would be subject to the same terms of settlement as other London-based equities. This “settlement” concerns the delay between the execution of a trade and the movement of funds from buyer to seller. Different settlement times across the two markets would otherwise be a problem, with the Shanghai exchange featuring a one-day delay relative to London. The need to fully work out these mechanisms explains the delay between the 2017 pilot study and the 2018 implementation. It remains unclear whether the Chinese depository receipts would be fully convertible into local Shanghai shares. In remarks included in the May 2018 China Securities Journal, Shenwan Hongyuan Securities analyst Lin Jin suggests that full convertibility is unlikely to be built into the initial structure of the Stock Connect. However, this would not preclude such convertibility being added later on.

An important milestone laying the groundwork for the Shanghai-London Stock Connect was the State Council's approval of the China Securities Regulatory Commission's CDR (China Depository Receipt) scheme on March 31, 2018. Interestingly, this same CDR scheme could also represent a way of enticing Chinese companies that had IPOs in the United States to establish a presence in Shanghai. The guidelines mandate a minimum market cap of ¥200 billion (or approximately $32 billion) for innovative firms that have an existing offshore listing, with eligibility extended to innovative companies not already listed overseas so long as they meet other criteria including minimum sales and profit levels. Notable Chinese companies that easily qualify, while currently having their shares listed only on the New York market, are Alibaba and Baidu. Following the approval of the new CDR scheme, in April 2018, Governor Yi Gang of the People's Bank of China not only confirmed that the new Stock Connect would be launched before year end but also announced a substantial expansion in the existing Shanghai-Hong Kong and Shenzhen-Hong Kong Stock Connects. Indeed, the daily limits for each of these quadrupled as of May 1, 2018, with new quotas of ¥52 billion and ¥42 billion, respectively. Although the quota limits for the Shanghai-London Stock Connect have yet to be revealed, the hefty expansion in the scale of the existing Stock Connects at least gives some suggestion that the Chinese authorities have become willing to allow for greater movements of funds.

Not everyone is optimistic about the new Stock Connect. For example, consulting firm Capital Economics has already derided the venture as representing “more hype than substance.” This is perhaps a bit premature given that it could not possibly have much substance until it is actually launched. Nevertheless, it would not be surprising if it took some time to induce meaningful new flows of funds between China and the United Kingdom. The volumes seen under the original Shanghai-Hong Kong Stock Connect themselves rarely challenged even the relatively low initial quota limits and it is quite possible the short-run impact of the Shanghai-London Stock Connect could be similarly underwhelming.

The potential long-run impact cannot be overstated, however. It is nothing less than a landmark step forward in China's integration with world financial markets. For the perils of underestimation of the consequences of such major moves, one need look no further than Henry Kissinger's remarks at the time of Richard Nixon's famous visit to China in 1972: “The maximum amount of bilateral trade possible between [China and the United States] … is infinitesimal in terms of our economy.” That is surely one claim he would like to have back!