Sir Jim Ratcliffe has written to Manchester United fans to ask for "time and patience" following the announcement of his minority investment at Old Trafford.

Ratcliffe, chairman of chemical company INEOS, has agreed a deal to buy a 25% stake for around 1 billion ($1.3bn).

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As part of the arrangement, INEOS will take responsibility for all football operations but Ratcliffe has warned supporters that, after a decade of decline, success is unlikely to return overnight.

"I wanted to write to you at this time given the critical role of the fans to the future of Manchester United as we recognise our responsibility as custodians of the club on your behalf, Ratcliffe wrote in an open letter to the Manchester United Supporters Trust (M.U.S.T.).

"I believe we can bring sporting success on the pitch to complement the undoubted commercial success that the club has enjoyed. It will require time and patience alongside rigour and the highest level of professional management."

Ratcliffe's arrival is the first major ownership change since the Glazer Family's takeover in 2005. Sir Dave Brailsford and Jean-Claude Blanc are expected to take the INEOS seats on the club's football board with the pair set to spend time at Carrington in January. The investment is still subject to regulatory approvals, which could take anything up to eight weeks.

"You are ambitious for Manchester United and so are we," Ratcliffe added in his open letter.

"There are no guarantees in sport, and change can inevitably take time but we are in it for the long term and together we want to help take Manchester United back to where the club belongs, at the very top of English, European and World Football. I take that responsibility very seriously.

"Please note that, as with any deal, it is subject to the usual regulatory sign-off process and therefore we do not expect to speak publicly about club matters until after the deal has completed."