Does the boarding port need to be in the country of visa issue?

I currently have a visa to travel to China that was issued in Switzerland. But I've realized that I may be better off starting (and ending) my journey in the UK.
Is this something that is allowed, or is there a need to travel from the country of visa issue?
Note that this question has already been asked regarding a Schengen visa. But since my question is for a China visa, I thought that it isn't an exact duplicate.
Best Answer
In general no country cares where you start your journey from.
Exceptions to this principle are very rare - for example if you were claiming to be escaping from the oppressive regime of country X but were transiting through country X.
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Why an airline might deny boarding to US visa holder?
If you are traveling on a tourist visa, the airline might stop you from boarding based on its suspicion that CBP will deny you entry because you don't intend to return to your home country or you intend to work in the United States.What are the reasons for denied boarding?
Non-Discriminatory Reasons For Being Denied Boarding- Being intoxicated or under the influence of illegal drugs.
- Attempting to interfere with the duties of a flight crew member.
- Disrupting flight operations or engaging in unruly behavior.
- Having an offensive odor that is not caused by a disability or illness.
What happens if you are denied entry to a country?
The range of options here include them applying your return flight to the flight on which they take you home without charging anything more, doing that but charging a change fee, or requiring you to buy a new ticket\u2014up to and including a full-fare, one-way walk-up ticket.What is a visa issued upon arrival?
Visa on arrival means that travellers must obtain a visa in order to enter the destination country, but it can be obtained upon arrival. Visitors do not need to apply for a travel visa beforehand. Visa required means that travellers must apply for a visa to the country before actually travelling there.These Countries will DENY ENTRY at Immigration. Vacation Disasters
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