Paywall, but The Times helped the investigation, so not unreasonable.
Gist is: Sugar tried to claim he was non-dom, to save £186m in tax. However, members of HoL are officially classed as residents (because Jesus, imagine someone deciding on the laws of the country while not even officially living there)
Additionally, he's quoted in the article saying that if he was aware, he would have stepped down...So his HoL membership is now being reviewed on the grounds that he was ready to drop his duties the moment it was convenient to him.
If I remember correctly too, the "travel days" don't count. Might have changed recently, as it was a law written for steamships, not private jets.
So someone could arrive on the first Monday flight, be there for Monday, Tuesday, Wednesday, Thursday, fly back Thursday evening.
Technically only two days in the uk, so they could be around for the bulk of 45 weeks, and still be non-dom.
There is a lot of obfuscation going on with tax systems. This is by design so that only those with money can take advantage of it. Crickhowell showing just this.