I am trying to reconcile a couple of interesting UK visa cases that I have read about on this site and others, pertaining to how the rules are interpreted regarding the purpose of one's visit. Specifically, this concerns the way in which possible visa abuse might viewed.
Consider these two examples to start:
In this case [Travelling on Business visa to UK for tourism purposes ], an applicant was issued a visa for a trip. This was canceled on medical grounds and they wanted to know if they could use the visa for an entirely different purpose. The answer given by one of the experts here was "Yes".
Similarly, in this case [Can I travel to the UK for business on a C visit visa? ], the person applying said that their visit was for tourism purposes, but wanted to make a business visit. Since the business activities are on the permitted activities list, the same expert said "Regardless of what you wrote down on your application, the Entry Clearance Officer approved you for everything on the permitted activities list. It's how the Standard Visitor Visa works."
In all cases, the controlling reference seems to be the Permitted Activities for All Visitors list in Appendix V of the rules.
However, there are instances where, if the premise of the visit changes (material change of circumstances) the visa becomes invalid. A quick search of this site gives a number of examples -- (1) change of job, (2) a large change in the length of visit (and consequently the purpose, as I understand), (3) bankruptcy, and so on. This is a great example: [Holiday visit to UK with a C-Visit visa which I got for a business trip that never happened; meantime I left the company that backed my application ], which is close to the present question.
It seems possible for the lines between these things to become blurred. Here's a for instance:
A traveler may apply for a visa to spend 10 days being a tourist, and while they are there, they could attend a business meeting on one of the days. On another immigration forum, I noticed a case where a tourist even attended a job interview [which are explicitly permitted by the rules]. Let's assume these meetings weren't declared in the visa application.
Here is my specific question:
When one is asked to declare the purpose of the travel during an application for entry clearance, to what extent is one bound to doing only those things described in the application?
It seems that the answer to the above question clearly is not "word for word", but surely it can't be "absolutely anything permitted by the rules". It seems to me that, taken to an extreme, the applicant could be deceptive about the purpose of the trip.
Also every deception example I've seen on the website are essentially open and shut cases, where there's essentially no defense, so perhaps this is all academic.