Amarin Corp Plc (AMRN)

[FlyFishingStocks]

Did he do it all the while staying under the 1 percent filing requirements ?

Yes, more than likely.
Tatsumakisamma gave the best description of how this occurs:

Only if his net ownership changes more than 1%. He can buy or sell 4 million shares before triggering that. He can sell 2 million of his $4.40 shares, book the loss and buy back 2 million of $1.3 shares every week and not need a 13D if he wanted. Square up in time for the 13F deadline and report no net change in shares. He can also collect premiums on loaned shares, sold options, etc and book profits off that that lower actual cost basis on his books, but none of that hits the SEC report. Doubtful the guy has been just sitting on his bag since last March when the SP tanked (who's to say he didn't help that himself to stir up shareholder anger to feed his proxy) and not actively traded this through various means to make money. Same games Baker Bros played.