Norris McWhirter, co-founder of the Guinness Book of Records with his identical twin Ross, died in Wiltshire, England, on Tuesday, BBC reported. He was 78.

McWhirter suffered a heart attack while playing tennis on Monday evening, his family told BBC.

Ross McWhirter, an outspoken critic of the Irish Republican Army, was assassinated by the terrorist group back in 1975.

Norris McWhirter, a man of strong political views like his brother, was also an athlete like him and worked for some time as a BBC sports journalist. He represented Scotland and Britain as a runner in the 1950s. He was also the timekeeper for his friend Roger Bannister, whom he had known since 1945, on the day he broke the four-minute barrier for the mile.

Sir Roger said, "Norris was a dear and staunch friend. It is really hard to believe he's gone." The two friends had dined together just last Saturday night, on the eve of the London Marathon.

The McWhirters set up the Guinness Book of Records in the mid-1950s.