Details of the deal, which values West Ham, including its debts, at £105 million, have not yet been revealed but Sullivan will invest between £40 million and £50 million with some of the money going to the creditors of former owner Bjorgolfur Gudmundsson, some to pay off a portion of the debt and the rest to be invested in the team.
West Ham and Portsmouth takeovers to move a step closerWest Ham Uniteds future back in the balanceAs part of the deal Sullivan - who has been given 'operating control' of the club although he cannot make any significant financial investments without the approval of Straumur - has an option to buy the remainder 50 per cent at a fixed price at any point in the next four months. If he does not do so within that timeframe then the price, it's understood, goes up.
Sullivan also reassured manager Gianfranco Zola that his job is safe although, it's understood by the Daily Telegraph, he has twice approached the former Manchester City manager Mark Hughes to see if he would eventually consider taking over.
However after consultations, Sullivan accepts that Zola is not only a good coach but a popular manager at the club and one who has not had sufficient backing in the transfer market.
West Ham will now move quickly to try and strengthen their squad with inquiries already being made for the Monaco striker Eidur Gudjohnsen and Manchester City's Benjani Mwaruwari who have both been linked to the club in the past. Both players are understood to be available.
Sullivan will also attempt to revive talks for West Ham to eventually move into the Olympic Stadium - something that Fernandes also wanted to do - and will even try and preserve the ground as an 80,000-capacity venue with plans to provide cheap tickets for OAPs and the disadvantaged. He has dubbed West Ham the 'people's club'.
Like Fernandes, Sullivan is a life-long West Ham supporter and he said he has a seven-year plan to take the club into the Champions League - the former chairman Eggert Magnusson also pledged to do this but Sullivan has insisted he will not repeat the profligate spending of the Icelandic regime although there will be significant investment.
"We have a seven-year plan to get them into the Champions League and turn them into a big club and over the seven-year period we do plan to spend a lot of money," Sullivan said. "The short-term plan is all about survival and getting behind the team. It is also about getting behind the manager.
Categorically he (Zola) is staying," said Sullivan. "We will be sitting down with him tonight to work on some transfer targets as we realise, as fans, that the team needs a few additions."
Sullivan stressed that taking over West Ham was the fulfilment of a lifelong football ambition. "We've got the club that we've always wanted," he said.
"We are West Ham fans and I don't think we would have bought West Ham if we hadn't been fans as, from a business point of view, it is in a serious mess.
'But we are deeply and passionately involved with West Ham. David was brought up opposite the West Ham ground. I was never popular with Birmingham fans because I admitted I was doing a job there to the best of my ability.
West Ham is a club we've always wanted to own and we've come back. It is nice to get the club back in the hands of east Londoners and these are exciting times. We hope to persuade the government to let us move into the new Olympic Stadium and I believe the people of east London would support that move."
Sullivan will take over as chairman - replacing Andrew Bernhardt who had been appointed when the company Cb Holding was created following Gudmundsson's financial collapse - with David Gold also expected to join the board and former Birmingham managing director Karren Brady appointed as a two-day-a-week, part-time vice-chairman.