The previous best score in the 100th Test belonged to former Pakistan batsman Inzamam ul Haq who hit 184, also against India in Bengaluru in 2005.
Root reached his double ton with a six over long-on off the bowling of R Ashwin.
This was Root's fifth double century and he is joint second among
Root is also only the ninth batsman to slam a century in his 100th Test.
Colin Cowdrey (104 vs Australia in 1968), Javed Miandad (145 vs India in 1989), Gordon Greenidge (149 vs England in 1990), Alec Stewart (105 vs West Indies in 2000), Inzamam ul Haq (184 vs India in 2005), Ricky Ponting (120 and 143 not out vs South Africa in 2006), Graeme Smith (131 vs England in 2012) and Hashim Amla (134 vs Sri Lanka in 2017) have earlier scored centuries in their 100th Test.
Root is also only the third cricketer to play both his first and 100th Test match in the same country he was touring.
Root had made his debut in Nagpur in 2012 when England won the series 2-1. Kapil Dev of India and Carl Hooper of West Indies are the other two cricketers to have done so.
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