UK conference speaking: what if it's my job?

OK, so we look at the visitor visa rules initially (these apply to US citizens entering either on a visitor visa, or the visa exemption). Under "permitted activities for all visitors, we find this section:

Business – general activities

5 A visitor may:

• (a) attend meetings, conferences, seminars, interviews;
• (b) give a one-off or short series of talks and speeches provided these are not organised as commercial events and will not make a profit for the organiser;
• (c) negotiate and sign deals and contracts;
• (d) attend trade fairs, for promotional work only, provided the visitor is not directly selling;
• (e) carry out site visits and inspections;
• (f) gather information for their employment overseas;
• (g) be briefed on the requirements of a UK based customer, provided any work for the customer is done outside of the UK.

So, it is understood that business visitors may come to the UK for all these activities (and a whole bunch more are permitted further down the list, provided they are within the same company, or a company that there is an existing business relationship with).

It is clearly understood that, as these visits are "on business" people will be receiving their normal salary for this. The person in question won't be deriving any personal profit from this, and in fact, neither is their employer, who has in fact paid for this privilege. This would seem to me to mean that there isn't any requirement to look at the additional rules for "permitted paid engagements".

However, I can imagine things being complicated somewhat if attending meetings and events was the only thing a person was employed to do. While obviously difficult to enforce, the general understanding for UK immigration is that business visitors will not continue to do their "normal" work while visiting, as that is not listed in the permitted activities section. This obviously gets more complicated if their "normal work" is attending events like this, as it gets harder to argue that permitted paid engagements are not relevant.

Of course, as with all immigration situations, there's a degree of interpretation on the part of the immigration officer that you have to deal with.

Furthermore, I am not an immigration expert, just someone with the rules in front of me (and having seen company reps at various conferences). Note that our resident ex-immigration lawyer appears to disagree with this assessment.

According to the visitor rules:

Business – general activities

5 A visitor may:
(...)
(d) attend trade fairs, for promotional work only, provided the visitor is not directly selling;

This seems to describe the situation in the question pretty well. Being paid by one's US employer is critically different from being renumerated by the organizers of the "conference" (which, if it is organized for profit and businesses pay steep fees to have their representatives present there to speak to attendees, sounds like something that is well described by the term "trade fair").

The fact that the US employer made a business decision to pay money for the traveler to have an official pulpit to deliver his message from would seem to me to make it more "promotional work", not less. They wouldn't do that if they didn't think it would bring in business down the line.

And the fact that the traveling speaker is simply spreading the good word about what cool things they do at company XYZ rather than taking orders explicitly, seems to be required for 5(d) to apply at all ("provided the visitor is not directly selling").

In practical terms, the way the money flows in this example ought to exclude any argument that the traveler is performing a service to the local organizers by speaking -- he's more a customer than a provider to them.