Several buyers reported problems with the system, and while business was brisk at the counters, issues with the vending machines and the suspension of the online system in the morning brought complaints.

Mr Kwok, who holds a first generation home return permit, said he had no choice but to buy his ticket at the terminus, but said as far as he knew “even the mainland’s vending machines can’t read the older generation home return permits”.

Was Hong Kong’s high-speed rail line to mainland China worth all the sacrifices?

Meanwhile, Mr Wong, who is a new migrant, said he tried to buy tickets via the mainland’s online ticketing system, but was told his purchase request had been denied for an unknown reason.

“I think the online payment failure I encountered showed that Hong Kong’s ticketing network is still not fully integrated with the mainland system,” he said.

About 6.8 million Hongkongers use home return permits, a travel document issued by mainland authorities for Hong Kong and Macau residents to cross the border, on a regular basis.

Ben Chan Han-pan, a pro-establishment legislator, and vice-chairman of the Legislative Council’s railways subcommittee, said it was not clear if the unsuccessful buyers were already on the mainland authority’s blacklist, or if they had just experienced glitches with the system.

The blacklist is part of China’s system for tracking untrustworthy people, and will include those banned from using the train for a variety of reasons, from smoking, to the speculative reselling of tickets, and “other behaviours”.

Chan said the Hong Kong government must get mainland authorities to clearly explain how their blacklist of people works, and give this information to the public.

“Will a passenger be [put on the list] for what he or she did in Hong Kong, such as areas outside the mainland port area in the West Kowloon terminus?” said the Democratic Alliance for the Betterment and Progress of Hong Kong member.

“And if a person has already been punished, can his or her name be taken out from the list? The government has the responsibility to learn about the [system] and make things clear to the public.”

No platform doors, but special measures to ensure no one falls on tracks at terminus

But Chief Executive Carrie Lam Cheng Yuet-ngor called on the public to be more understanding about issues faced by the multibillion-dollar project.

“Overall, the first day of ticket sales yesterday has been smooth, but I totally understand the obstacles or the hiccups the citizens faced when they bought the tickets,” she said on Tuesday, ahead of her weekly Executive Council meeting.

“I hope citizens will be understanding about that as the express rail link is a unique and complicated project.”

She said the railway was a cross-border project that would require integration with the railway network on the mainland, and time was needed for the necessary adjustments.

A spokesman from the Transport and Housing Bureau said the MTR Corp has to follow the rules of the mainland’s blacklisting system, because the line is a cross-border railway jointly operated by the mainland and Hong Kong.

However, a person deemed “dishonest” by the mainland authorities can still visit unpaid areas in the West Kowloon terminus, and can still have unaffected access to public services in Hong Kong, according to the spokesman.

The spokesman said: “No matter if a passenger purchases [express rail link] tickets in Hong Kong, or in the mainland, his behaviour in the West Kowloon Station, and on the train, will be regulated by passengers’ rules jointly set out by Hong Kong and mainland operators, and MTR By-laws.”

According to the passengers’ rules, the MTR Corp may refuse to sell a ticket to a passenger if he is deemed unfit for travel under the relevant laws or regulations.

In a separate event, close to 100 police officers, firefighters and ambulance officers were deployed for a drill along Wui Man Road near the West Kowloon terminus to prepare for the railway’s opening.

The exercise simulated a road accident caused by a bus driver who had a heart attack. The bus lost control and mounted the pavement, hitting a pedestrian, and causing a car to turn over. The rescue team showed how to work with each other and rescue the injured.

A police spokesman said the drill also involved closing roads, so it required effective coordination with the Transport Department, and the MTR Corp, for alerting passengers to any delays.

What is the blacklist and how do you get put on it?

In May, China Railway Corporation issued a list of seven types of bad behaviour that would result in a ban from its vast mainland high-speed network, and a punishment of not being able to buy railway tickets for 180 days.

The behaviours included smoking on trains, faking documents for rail travel, speculative reselling of tickets, flouting rules at the terminus, and causing disruptions. But, the list also cited “other behaviours subject to administrative penalty according to relevant laws and regulations on the mainland”. The rail operator has not elaborated on what those “other behaviours” might be.

Since 2014, Beijing has built up a data-driven social credit system that assesses the trustworthiness of each Chinese citizen, business and authority and generates ratings for them. The ratings affect everything, from their access to services, such as taking trains and flights, to being approved for a loan.

Last month, the mainland rail operator added 242 people to its list of defaulters.