You must be able to show that: you are seeking entry as a visitor for no more than six months; and you intend to leave the United Kingdom on completion of your visit; and you have sufficient funds to maintain and accommodate yourself without working or recourse to public funds. Remember if you are a visa national you will require a visa to enter the United Kingdom.
You will need to complete an application form. Applications, except those for asylum and work permits or under EC law, will not be valid unless they are made on the appropriate application form. You are free to transact business in the United Kingdom either as a tourist or in connection with your employment or business overseas. You may not: take paid or unpaid employment either for someone else or on your own account; produce goods or provide services within the United Kingdom; or sell goods and services to members of the public. You may: attend meetings with United Kingdom businesses or negotiate and enter into contracts with them; and attend trade fairs, conferences and classroom training. You may also enter as a visitor if you are a sports person or entertainer coming to the United Kingdom for a trial or audition and for a personal appearance which does not involve a performance. The maximum allowed as a visitor is six months. Frequent business visitors can apply for a multiple entry visa as a visitor valid for two years or even 5 years.