U.S. activist investor Elliott Capital Advisors has amassed a 13.2 percent stake in British discount chain Poundland Group Plc, according to a UK regulatory filing on Thursday.

On Wednesday, Poundland agreed to be bought by South African retailer Steinhoff International Holdings NV for about $800 million, giving Steinhoff more than 900 shops in Britain, Ireland and Spain.

It is the biggest takeover of a listed British company since a vote on June 23 to leave the European Union.