Planning for the Hong Kong section of the Guangzhou–Shenzhen–Hong Kong Express Rail Link began in earnest in April 2007, when the Executive Council assigned the task to the MTR Corporation. The project was ambitious: a fully underground corridor, 26 kilometres of tunnels, connecting Hong Kong's rail network to China's rapidly expanding high-speed rail system. Cost estimates came in at HK$39.5 billion — roughly US$5 billion — with the government projecting economic benefits of HK$83 billion over fifty years from time savings alone.

Funding approval from the Legislative Council came in January 2010, but the construction that followed was troubled. Delays accumulated. Budgets overran. The opening, originally targeted for an earlier date, was pushed to 23 September 2018 — seven years after construction began. Critics pointed to poor oversight. Supporters said the scale and complexity of the underground engineering were simply extraordinary.

When the line finally opened, it delivered on its core promise. Travel time between Hong Kong and Guangzhou South — a journey that once required switching trains at the border — fell to around 47 minutes under ideal conditions, though trial runs suggested a more realistic figure of about 78 minutes. Either way, the contrast with what came before was stark: the old Guangzhou–Kowloon through-train had taken roughly two hours.

The XRL connects Hong Kong's single station, the West Kowloon Terminus, to three intermediate stops on the mainland — Futian in Shenzhen, Shenzhen North, and Humen — before reaching Guangzhou South. From there, connections extend across China's vast high-speed network: north to Beijing, east to Shanghai and Hangzhou, deep into cities that had once been a full day's journey from Hong Kong. By 2024, the line was carrying an average of 88,800 passengers a day, with long-distance sleeper services to Beijing and Shanghai added in June of that year.

The arrangement that generated the most controversy was not the cost overruns but the legal framework. Under legislation passed in June 2018, Chinese customs and immigration officers operate within the West Kowloon station, and the areas they occupy — including the train compartments — are subject to mainland Chinese law. This was the first time Chinese criminal law had been enforceable on Hong Kong soil, and critics argued it represented a fundamental erosion of the one country, two systems principle that had governed Hong Kong since 1997.

The Hong Kong government and Beijing defended the co-location arrangement as a practical necessity for seamless cross-border travel. Protests had erupted years before the station even opened: more than a thousand people demonstrated against the project in November 2009, and a larger demonstration surrounded the Legislative Council Building in December of that year when the funding application was being debated. The funding passed. The station was built. The legal anomaly remains.

In January 2020, the line closed due to the COVID-19 pandemic and the border restrictions between Hong Kong and mainland China. It did not reopen until January 2023 — a three-year gap that left West Kowloon Terminus largely silent during a period when Hong Kong itself was struggling through its most politically turbulent years. When services resumed, they did so for a city that had changed considerably.

By 2024, the original Guangzhou–Kowloon through-train services — the older conventional railway that had connected the two cities since the colonial era — had been discontinued, replaced entirely by the high-speed link. The Express Rail Link is now the primary physical connection between Hong Kong and the mainland rail network. It is also, in a precise legal sense, the place where Hong Kong ends before you've left.