Norris McWhirter, co-founder of the Guinness Book of Records, has died aged 78, his family announced on Tuesday.
McWhirter was a regular contributor to TV's record Breakers
McWhirter suffered a heart attack while playing tennis at his Wiltshire home on Monday evening, his family said.
During the 1970s and 1980s he was a fixture of the BBC One children's show Record Breakers, hosted by the late Roy Castle.
McWhirter, whose identical twin brother Ross was murdered by the IRA in 1975, had also been a successful athlete and worked as a BBC sports journalist.
Like his brother, he also held strong political views.
McWhirter joined TV's Record Breakers in 1972
McWhirter's family said in a statement: "Norris cared passionately about
Great Britain, democracy and the rule of law and was always active in politics,
but usually behind the scenes.
"The two things he attached most importance to were the freedom of the
individual and the sovereignty of the United Kingdom.
"Apart from his family, his great loves were visiting the 1,049 offshore
British islands and having a good game of tennis. He was energetic to the
McWhirter, an all-round sportsman, represented Scotland and
Britain at running in the 1950s.
He was also a time-keeper for his friend Sir Roger Bannister on the day he broke the first four-minute mile.
Paying tribute, Sir Roger said: "Norris was a dear and staunch friend.
"We had known each other since 1945 - nearly 60 years - and we were dining
together just last Saturday night before the Marathon."
He added: "Many disagreed with his views but his integrity was never in doubt," he
"My family and I will miss him more than I can say, as will his own family. He was a human dynamo. It is really hard to believe he's gone."
With brother Ross Norris set up the Guinness Book of Records in the mid-1950s.
Ross McWhirter, an outspoken critic of the IRA, was shot dead by the group after offering a large reward for information leading to the capture of IRA bombers.
Speaking about the murder in a TV programme in 2002, Norris McWhirter
said: "I felt not so much bereaved but it was an amputation.
"You had sort of lost part of you - it is a very difficult thing to
Ross McWhirter was shot dead by the IRA in 1975
The twins held trenchant views and were vocal on a number of issues, including Northern Ireland.
They founded campaign group the Freedom Association, which campaigned strongly against British involvement in the European Union and other areas.
Both had enjoyed successful athletics careers before entering journalism and joining the BBC as sports
They co-presented Record Breakers, which first hit the nation's TV screens in 1972.
It was as the show's resident records expert that Norris McWhirter was best known
to children of the 1970s and 1980s.
Each week he would answer from memory any question about records that the
audience chose to ask, and the exchanges were never rehearsed.
Annual editions of the Guinness books, cataloguing human and natural extremes, have become best-sellers in many countries.
McWhirter continued to edit the volumes until 1986, remaining as advisory editor until 1996.
By 1999, the book had been translated into 37 languages and sold more than 87
million copies around the world.
Claire Folkard, the current editor of Guinness World Records,
expressed the organisation's sympathy to the McWhirter family.
"Last summer he joined us at our party at the Tate Modern to celebrate the
book's 100th millionth edition and he was the most popular guest in
attendance," she said.
"He was a joy to work with and inspired all of those he came into contact
McWhirter is survived by his wife Tessa, daughter Jane and son Alasdair.