I can't be bothered to find the source but it might be Henley & Partners who advise on relocation tax and rules. China was #1 in millionaires leaving home domiciles but the UK was second, which is more than a bit scary when you consider the relative population sizes. There are roughly a billion Chinese people and even the highest estimates put the UK population at 73 million.Therefore, the UK is losing wealthy people faster than anywhere else in the world.
Absolutely fine to declare, shut the door on the way out. But the reality is that the UK has lost an asset who would have paid a significant amount of tax, to help fund education and the NHS, and won't get the money back again.
We're not ultra high worth people, but we are just successful enough to think we should preserve what we've earned and parental enough to want to pass it down to DC. That is, IMO, the thin line -- and the art of government and taxation is to take a sensible share but not more. Where that line is drawn looks very different depending on the commercial risk a person or couple took to make the money. In self employment as a freelance writer, I was able to cover our day to day costs and mortgage while DH built a business.
Old rules still work:
1 The first year you pay for the business
2 The second year the business pays its way
3 The third year, the business starts to pay you a wage. But probably not a pension contribution; that comes in year five or six. And after that, reinvestment and pension contributions are the priority. Until you retire.