What documents are needed for entry on a UK visitor visa and can I travel with different passports?

The post inquires about the necessary documents for entering the UK on a visitor visa, mentioning that the visa was obtained four years ago. It also addresses the situation of a non-Thai wife needing to use an old passport to exit Thailand while re-entering with a new passport, questioning whether the airline requires matching passport numbers. Comments suggest practical solutions for handling passports at check-in and immigration, emphasizing the importance of carrying both passports and clarifying that the passport used for the airline ticket does not have to match the travel document presented to immigration.