You are right. Choosing a foreign bank in the UK is of no help at all. Interest on money which is anywhere in the UK is subject to UK tax. So is interest on money anywhere else, which HMRC are adept at finding out about. He is more likely to end up (along with another 80,000 people who don’t know what’s about to hit them) with heavy fines or a prison sentence by trying to avoid tax on interest – unless he avoids putting it anywhere in the European Economic Area, or in any counry with which the UK has a tax treaty. That leaves him with very little choice beyond a handful of countries that nobody in their right minds would deposit so much as a used handkerchief in.