Some conference attendees and accompanying persons will need to apply in advance for a Standard Visitor Visa to enter the UK. You can apply for a Standard Visitor visa if you want to visit the UK for business-related activities, for example: you’re coming to the UK for a conference, meeting or training.
Document requirements vary depending on your nationality. For specific information on travel documents, whether you need a Visa to enter the UK and how to apply for a Visa, please visit https://www.gov.uk/check-uk-visa
The earliest you can apply is 3 months before you travel.
Example: If you plan to travel on 16th July 2022, you can apply for a visa from 16th April 2021
You should get a decision on your visa within 3 weeks when you apply from outside the UK.