DaveScott

Thanks for your helpful reply, K.Samran.

Your first answer was fine. As you say, the Visa is not required when entering the UK with a British passport. I was basically worried about the Visa confirmations made at the Thai end - usually, my wife's passport is checked very carefully for this at passport control.

In response to Festers post - a further question with respect to my daughter who is only 3 months old, and holds Thai and British passports:

If the Thai passport is used to exit Thailand for travelling to England, is a Visa required?