FORMER Manchester United boss Sir Alex Ferguson, the most successful manager in the history of the British game, is seriously ill in intensive care after undergoing emergency surgery following a brain haemorrhage.

Good wishes immediately flooded in after his former club, where he spent more than 26 years in charge, announced the news in a brief statement yesterday evening.

The club said the procedure had gone “very well” but that the former manager would need a period of intensive care to aid his recovery.

Rumours began to circulate about the 76-year-old’s health after Doncaster manager Darren Ferguson, Sir Alex’s son, did not attend his side’s final match of the League One season against Wigan because of what was reported as a “severe family issue.”

The FA, Premier League, Fifa, Uefa and individual clubs from Britain and around the world tweeted their best wishes along with a host of current and former United players.

David Beckham posted a picture on Instagram of him signing a contract as a teenager alongside Ferguson, accompanied by the message: “Keep fighting Boss... Sending prayers and love to Cathy and the whole family.”

Former United striker Wayne Rooney wrote on Twitter: “Get well soon Boss. Thoughts with all the family at this sad time.”

And Cristiano Ronaldo, who was signed by Ferguson as an 18-year-old in 2003, said on the social network: “My thoughts and prayers are with you, my dear friend. Be strong, Boss!”

Ferguson retired in May 2013 after winning 38 trophies during 26-and-a-half years as manager.

He had a prolific career as a striker in Scotland but it was when he entered management that his true talent in football became clear.

After transforming St Mirren, Ferguson took over the hot-seat at Aberdeen and guided them to the European Cup Winners’ Cup in 1983, beating Real Madrid in the final.

Ron Atkinson’s sacking led to Ferguson taking over at Old Trafford in November 1986.

The highlight was United’s treble of Premier League, Champions League and FA Cup in 1999, and he went on to achieve more European glory in 2008 as well as 13 league titles.