Unlike other countries, the UK does not require flight and hotel reservations for the Visitor Visa application. They used to request these records but ceased doing so years ago.

That is because it is simple to book and cancel reservations. Even if they are paid for, hotel and airline reservations reveal nothing about the traveller's desire to leave the country — a crucial factor in determining whether to grant a visa. After all, it's simple to decide not to take the return trip. Hence, at the point of the Visitor Visa application reservations do not serve as strong proof of your intention to leave the UK at the end of your desired stay.

The Home Office instructs explicitly not to provide those documents because they do not want to be liable for the missed flight and hotels if the visa application is delayed. They also understand that travel plans may alter, and visitors may choose to come at different times for a different conference/meeting/course and greatly allow such flexibility.

However, it is crucial to book your plane tickets and accommodation after you successfully get your Visitor Visa. That is because when you cross the border with the UK, the Border Force officer may want to see proof of your hotel and flight details. They will make the decision on the spot on how genuine your trip is and how likely you are not to remain in the country at the end of your intended visit. Unlikely other countries, if the UK Border Force officer is suspicious of your intentions, even if you hold a valid visa, they have the right not to let you in the country. Hence, having a clear reason and corresponding reservations/emails is crucial when you get your Visitor visa and plan your trip to the UK.