Upvote:4
As long as you're employed by a company in the US, there is a great deal of work you can legitimately do for your company on a short trip to the UK as a visitor, which is covered in Appendix V rules. You do not need to obtain a visa before arrival as long as your activities are covered.
General business activities might cover you in terms of just attending some meetings:
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.
If you are specifically visiting another part of your own company, e.g. you are from the New York branch of Widgets Incorporated and you are visiting the London division, there's more detail:
Intra-corporate activities
6 An employee of an overseas based company may:
(a) advise and consult;
(b) trouble-shoot;
(c) provide training;
(d) share skills and knowledge; on a specific internal project with UK employees of the same corporate group, provided no work is carried out directly with clients.