It took Ferguson six years, and cost him many, many millions more than it might have done to land a player he feels can become the best central defender in the world.

Ferguson first spotted Ferdinand as a 17-year-old playing for a Bournemouth team managed by his close friend Mel Machin.

"We saw him at Bournemouth and I telephoned Mel and told him I was going to put a bit of money his way," said Ferguson.

"But he told me he wasn't their player and was on loan from West Ham.

"When he went back to West Ham we made a bid, but they said 'no'" admitted Ferguson, who failed in a second attempt to land Ferdinand.

"At the time he left to go to Leeds we had an opportunity to sign him but the timing wasn't right for us and we weren't ready for it.

"We had Ronny Johnsen and Jaap Stam as the regular central defenders at the time and Wes Brown coming through.

"But mid-season signings are not always suitable for me.

"I've never done a lot, normally I always make mid-summer signings," said Ferguson.

The Manchester United manager is confident his �30m investment will be a sound one.

"At 23 there's great potential. We're hoping he will mature here and develop into the best centre-half in the world.

"I know this is going to be a big challenge but want to prove my doubters wrong.

"I want to fulfil every bit of potential I have got. I know the management will work me hard here and get the best out of me."

Ferdinand attempt to hold out an olive branch to Leeds' supporters, but accepted he may get a rough ride when he returns to Elland Road with his new club.

"I would like to pay a big thank you to all the Leeds supporters," said Ferdinand.

"I'm happy I went there because they brought me on as a player.

"I'm not sure if they will forgive me. You have to ask them that.

"I hope I will get the sort of reception from them that I get when I go back to West Ham.

"But if not, then you have to be big enough to take it on the chin."