My son only holds a UK passport, although he was born and has lived all his life in Thailand. His mother, my wife is not Thai.
He's visited the UK a few times, but always with both me and my wife. Later this year I'm taking him to the UK for a 2-week holiday, without his mother (too difficult to get her another UK Visitor visa).
Will I need any letter or other documentation from my wife in order to take me son for a UK holiday? If so, can it just be a free-form letter in English and signed by her, or does it need to be more official?
Thanks.