Just thought I would let you know about a recent problem my husband had transferring his visa to his new passport. When he arrived at immigration the staff refused to transfer his visa as they said they had no proof that his old passport had been cancelled. Luckily we had an email contact at the passport office in Hong Kong and explained the problem. She sent a reply via email which he printed and took to immigration the next day. After much ado the staff agreed to transfer the stamp over but advised my husband that in future they would not do this without written confirmation from the British Embassy that old passports had been cancelled. The passport office website clearly states that once a new passport is issued the old one is cancelled however, quoting the words of the member of staff at immigration "it may be cancelled British style but it's not cancelled Thai style". It is worth alerting other British Nationals that they will have the same problem.