Veteran BBC broadcaster Sir Terry Wogan has died aged 77, after a short illness, his family has confirmed.
In a statement, they said: "Sir Terry Wogan died today after a short but brave battle with cancer.
"He passed away surrounded by his family. While we understand he will be missed by many, the family ask that their privacy is respected at this time."
BBC director general Tony Hall said: "Terry truly was a national treasure."
Sir Terry leaves wife Helen and their three children. The couple also had a daughter who died in infancy.
Limerick-born Sir Terry had a 50-year career on radio and television, including presenting Wake up to Wogan on BBC Radio 2 and the Wogan chat show on BBC1.
He was also the voice of Eurovision in the UK for many years and had been involved in the Children in Need appeal since it began in 1980.
BBC Radio 2 controller Bob Shennan said he was "one of the greatest and most popular radio hosts this country has ever heard", adding: "His millions of listeners adored him, as did his whole Radio 2 family. We will miss him enormously and our thoughts at this very sad time are with Helen and all the family."
Lord Hall said: "Terry truly was a national treasure. Today we've lost a wonderful friend.
"He was a lovely, lovely man and our thoughts are with his wife and family. For 50 years Sir Terry graced our screens and airwaves. His warmth, wit and geniality meant that for millions he was a part of the family."
Sir Terry originally went into banking after college before switching careers to join Ireland's national Radio Eireann as a newsreader and announcer.
He moved into light entertainment, as a DJ and host of TV quiz and variety shows in Ireland, before joining the BBC, where he would stay for the rest of his career.
He presented the breakfast show from 1972 to 1984, as The Terry Wogan Show, and then from 1993 to 2009 as Wake Up To Wogan.
He built up a firm fanbase, dubbing his audience the TOGs, or Terry's Old Geezers and Gals.
When he broadcast at breakfast for the final time, he told listeners: "The years together with you have not only been a pleasure but a privilege. You have allowed me to share your lives with you.
"When you tell me how important I have been in your lives it's very moving. You have been every bit as important in mine."
Colleagues of Sir Terry from BBC Radio 2 have paid tribute to him.
Simon Mayo described him as a "radio genius", saying: "The staple of all great radio is the friend behind the microphone - and he was the ultimate friend behind the microphone."
Ken Bruce said: "The voice which has been with us all our lives, in many cases, is no longer there... He was part of the fabric of our lives in so many ways."
Jeremy Vine said Sir Terry was "probably the greatest broadcaster since the invention of the microphone".
"He lived for the red light and the sense that there was a listener at the end of the microphone. He only ever spoke to one person, because the greatest radio is intimate."
A gift for sounding natural
By David Sillito, media and arts correspondent
There's a wonderful archive recording of the day President Kennedy visited Ireland in 1963.
The man capturing the scene for RTE - of people pushing past the police cordon - is a young Terry Wogan.
His accent is a little stronger, but he is definitely the Terry Wogan that was still broadcasting 50 years later.
The man you met off camera was very much the man you heard on air and it was obviously a gift - a gift for sounding natural, real.
Fellow Radio 2 presenter Paul O'Grady says there was no falsehood about him and that captures it perfectly - people can sniff out inauthenticity in a second and whether you liked him or not, there was nothing phony about him.
However, what made that extraordinary is that he could access that wit and apposite comment again and again, year after year, in front of huge audiences on Children in Need and the Eurovision Song Contest.
Live broadcasting is terrifying - things are always going wrong and a poorly chosen word or a comment that misses the mark can haunt you for years.
Yet with Sir Terry, I can't think of one. It's a clever man who can make that look easy.
Graham Norton, who took over as Eurovision commentator from Sir Terry, said on Twitter: "He made it seem effortless and for a young boy in Ireland he made it seem possible. RIP Sir Terry Wogan."
Current breakfast show host Chris Evans wrote: "We are all so terribly sad upon hearing of the passing of Terry. I can't put into words how the whole Radio 2 family is feeling."
Tony Blackburn said: "He was part of our lives, a real radio legend. He loved what he was doing and he gave an enormous amount of pleasure."
Dermot O'Leary said that, growing up in an Irish family, Sir Terry was "a signpost of home".
He described Sir Terry as "one of the foundations of broadcasting in this country", adding: "You feel his presence around Radio 2... He's the bedrock of the place."
Bond star Sir Roger Moore praised Sir Terry's charity work, tweeting: "Terry was the most brilliant fundraiser. My fav memory was when someone bid 75k for CIN [Children in Need] to have lunch with us both. A privilege."
Dara O Briain tweeted: "Terribly sad news about Terry Wogan dying. Hard to quantify what he achieved, not just in broadcasting but for the Irish in Britain.
"Hard to separate what he achieved & the accent he did it in, from the times in which he did it. And opened to the door to all who followed."
Tess Daly, who presented Children in Need alongside Sir Terry, said: "So, so sad at the news Sir Terry has passed away. He was the funniest, kindest man, it was a huge privilege to work with him & a joy to know him."
Prime Minister David Cameron wrote on Twitter: "My thoughts are with Terry Wogan's family. Britain has lost a huge talent - someone millions came to feel was their own special friend."
President of Ireland Michael D Higgins said: "Always proud of his origins in Limerick, he made many returns to his native country for television and radio projects.
"His rise to the top of radio listenership in the United Kingdom was a great tribute to his breadth of knowledge and in particular his unique, very personal sense of humour."
BBC Radio director Helen Boaden said: "He was an extraordinary broadcaster but also incredibly good fun, and will be sorely missed."
Sir Terry made his BBC debut on the Light Programme, now Radio 2, and in 1969 was asked to stand in for Jimmy Young on the mid-morning show, which led to a regular afternoon slot.
He took over the breakfast show on Radio 2 in 1972 and was an immediate hit.
Sir Terry first covered Eurovision for television in 1973 and from 1980 to 2008, he provided the commentary every year for the BBC.
His chat show, Wogan, ran from 1982 to 1992, eventually being broadcast three times a week. During that time, he also hosted quiz show Blankety Blank.
Sir Terry anchored the Children in Need appeal from when it was first broadcast, continuing to host it after retiring from regular broadcasting.
Stevie Spring, chairman of Children in Need, said: "Most people know him as the face of Children in Need, but he's the heart of the charity and has been for 35 years."
In 1992 he returned to the Radio 2 breakfast show, after a break of nine years. He announced his retirement in September 2009, making his final regular appearance three months later.
From February 2010, he hosted a live show on Sunday mornings for the radio station.
Sir Terry was last on air on Radio 2 on 8 November 2015.
For continuing coverage, watch the BBC News Channel and listen to BBC Radio 2.
The One Show: A Tribute to Sir Terry will be broadcast at 19:00 GMT on Monday 1 February.
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