Manchester United fans are "impatient" for the club to succeed, Sir Jim Ratcliffe said minutes after completing the London Marathon.
The club's billionaire owner told the BBC's Gabby Logan that he is trying his best to rebuild the club after more than a decade of relative inadequacy.
The 71-year-old said it was understandable that fans may be worried for the future but that it "wasn't a light switch, you can't just turn it around like that".
Sir Jim was speaking after breaking his personal best for a marathon with a time of 4 hours, 32 minutes and 52 seconds.
