Chris Patten, Hong Kong's last governor before the city was handed back to China in 1997, has undergone major heart surgery, the BBC reported on Tuesday night.
"As is well known, I underwent angioplasty while in Hong Kong [at Queen Mary Hospital in February 1993] and a cardiac ablation procedure some seven years ago; and since then I have been regularly assessed by my cardiologist," Patten, 69, said in a statement.
"Last year, for example, I had both a cardiac scan and a treadmill test. But on April 27, I experienced serious chest pains and was admitted to Chelsea and Westminster Hospital that night. I was transferred on April 28 to Royal Brompton Hospital where I was successfully treated with a combination of bypass surgery and angioplasty.
"These procedures have been successful and have ensured no permanent damage to my heart."
Nevertheless, Patten has decided to stand down from his 110,000 pound (HK$1.4 million)-a-year role as chairman of the BBC Trust with immediate effect.
"On the advice of my doctors ... and having consulted my family and friends, I have concluded that I cannot continue to work at the same full pace as I have done to date," Patten said. "On this basis I have decided with great regret to step down from the most demanding of my roles - that of chairman of the BBC Trust."
Vice-Chairman Diane Coyle would take over as acting chairman until Conservative peer Patten’s successor is named, the BBCs said.
Patten, who was Hong Kong governor from 1992 to 1997, made a visit to the city in March in his capacity as chancellor of the University of Oxford.
In an interview on RTHK, he was asked if he believed Hong Kong people would ever rule their own city. "Yes, I do, and I suspect sooner rather than later … even though democracy ... has been given a bad press in the last few years," he replied.
Since late 2012 Patten had spent much of his time dealing with the fallout from revelations that Jimmy Savile, once one of the BBC’s biggest stars, was among Britain’s most prolific sex offenders.
That was followed by other scandals including a BBC television report wrongly accusing a politician of paedophilia, and the resignation of the broadcaster’s director general after just 54 days.
Patten was previously chairman of Britain’s Conservative Party and was once seen as a future party leader but lost his parliamentary seat in elections in 1992.
Patten sparked debate on his last visist to the city when he revealed that the "biggest regret" of his tenure was that Britain didn't go further to implement parts of the Sino-British Joint Declaration, particularly on elections, prior to the handover.
Signed in 1984, the declaration guaranteed Hong Kong's social and economic systems for 50 years. It said the chief executive would be appointed by Beijing based on "elections or consultations" and that Hong Kong's legislature would be elected.
Patten's attempts to increase democracy by allowing more Hongkongers to vote for lawmakers in functional constituencies saw him dubbed a "sinner of the ages" by Beijing's Hong Kong affairs chief, Lu Ping.
Patten said London spent too much time negotiating on "areas that the Chinese leadership was never going to agree to, rather than simply taking action on those points". He added: "The only thing [Hong Kong] doesn't have is the right to elect its own government, and sooner or later it will have … anybody who tries to resist that is, I think, spitting in the wind."
He also said it would be a "concern" and bad for the city and country if Hong Kong's independence was eroded by mainland organisations.