18 May, 11:09
IRFU Chief Executive Philip Browne has issued a statement following confirmation of Ronan O'Gara's decision to retire from playing professional rugby.
He gained the first of his 25 Ireland caps in 1947 against France. He had previously appeared for Ireland in the uncapped games against France, England, Wales and Scotland in 1946.
Mullen was first choice for the 1948 Five Nations Championship and while Ernie Strathdee captained Ireland for the opening game against France, Mullen took over for the remainder of the tournament.
Under his captaincy, Ireland won a famous Triple Crown and Ireland's first ever Grand Slam victory.
It was a fitting tribute that he and the rest of the surviving members of the 1948 team were able to witness the Ireland team repeat the feat in this year's RBS 6 Nations Championship.
Speaking about the famous 1948 victory in Ravenhill, Dr. Mullen said: "We were tense and anxious, yet I knew and the players knew we could win.
"Every man had his say, it was an important part of the pre-match preparations in a side whose hallmark was team spirit."
Mullen was a noted tactician and acknowledged as a leader at a time when the captain set the tone for how the team played.
He led Ireland to a second Triple Crown in 1949 and was also selected as captain for the British & Irish Lions tour to New Zealand and Australia in 1950, playing an incredible 17 games on the tour including three Test matches.
At the end of his playing career, he continued to be involved in the game and had a noted administrative career which included serving as President of the Leinster Branch (1963/64) and also as Chairman of the Irish selectors.
IRFU President John Lyons said: "I would like to express my personal sorrow and that of the Irish Rugby Football Union on the sad passing of Karl Mullen.
"He was one of the great heroes of Irish rugby and leaves a lasting legacy for his contributions as a renowned hooker for Old Belvedere, Leinster, Ireland and the Lions and also for his input after his distinguished playing days as a committed and enthusiastic administrator of the game.
"I had the privilege of playing for Bective Rangers against Karl and I witnessed at first hand his great leadership and skills on the rugby field. I extend the sympathies of Irish rugby to his family.'"
Karl Mullen 1926-2009 RIP