The 75p-a-share deal comes at a 48.5 per cent premium to the group's closing price on 25 January, the last day before news of the offer seeped into the market. Ken Ford, the deputy chairman and former chief executive, will receive more than pounds 2.2m for his stake.
Landsbanki said it intends to run the UK broker independently and that it will keep the management team and chairman, Lord Baker, in place after the deal.
The Icelandic bank bought a 9.3 per cent stake in Teathers yesterday and said it had received acceptances of its offer from shareholders representing a further 48 per cent of the group's equity. Halldor J Kristjansson, the group managing director of Landsbanki, said: "The acquisition of Teathers will be a significant milestone in our international expansion strategy ... and provides an ideal platform from which Landsbanki can expand its activities into this market."
Lord Baker, a home secretary during Margaret Thatcher's premiership, said: "Landsbanki's cash offer is at a significant premium to the share price immediately prior to the announcement that Teathers was in discussions with a third party.
"The Teathers board has been given assurances that Teathers' management structure, management team and culture will be maintained. At the same time, Teathers will have access to additional capital and the Teathers board."
Teathers is in discussions with the Financial Services Authority about its involvement in the split capital investment trust sector. It was one of four firms excluded from the pounds 194m Christmas Eve settlement.