Root surpassed Cook's tally of 33 Test hundreds for England.
Joe Root etched his name in the history books on Saturday (August 31) by setting a new England record with his 34th century in the longest format during the second Test against Sri Lanka at Lord’s.
Root’s brilliant knock of 103 in the second essay followed his first innings score of 143, taking England’s total to 251 on the third day.
Root’s century was a historic moment for English cricket. By reaching his 34th Test ton, he surpassed the previous record of 33 held by former England captain Alastair Cook.
Interestingly, Cook was on-air when Root notched up his milestone and had a heartwarming reaction to the moment.
Speaking on the BBC Test Match Special commentary, Cook hailed Root as 'England's greatest' and a 'genius' for his craftsmanship at the crease.
"He is quite simply England's greatest, and it is absolutely right that he should have this record, on his own. Take it in, Joe. We are watching a genius," Cook said.
"I do not think there is a batsman that I can remember watching play (who shares) the sense of inevitability about scoring runs that Joe Root gives off. I called it when he was on about 6 today, that he was going to get 100. I know he is in great form, but it is just a pleasure to watch a master, a craftsman at work," he added.
Cook recalled Root's early days, including their first encounter in a List A match back in 2009.
"He could not get the ball off the square. Everyone said, 'he's a good player', but I did not see that," Cook stated.
Three years later, Cook was England's captain when Root made his international debut in the fourth and final Test of the 2012 India tour in Nagpur.
Joe Root returned with knocks of 73 and 20* in his debut match and left a lasting impressing on Alastair Cook.
"The only check was when he walked out to bat for the first time, how he would handle it. The game was in the balance and he walked out to bat with his England cap on, looking 13, massive smile on his face. I watched his first few balls, and I was like, 'This bloke is here to stay.' I honestly said, 'He's scoring 10,000 runs.' I don't know who I said it to, but I know that I said it," he concluded.
Root has played 145 Test matches so far, amassing 12,377 runs at an average of 50.93, including 34 hundreds and 64 half-centuries. His highest individual score in Test cricket is 254.
Coming to the second Test, Root’s second-innings ton put England in a strong position as Sri Lanka need 483 runs to level the series after the hosts won the first Test at Old Trafford by five wickets.
The visitors were 53/2 at stumps on Day 3, with Dimuth Karunaratne (23) and Prabath Jayasuriya (3) unbeaten in the middle.