Yes, easily.
But unfortunately for Sunny, some bad captaincy decisions from the Indian captain Venkatraghavan screwed the pooch with all his efforts just ending in a draw that pushed that score way behind in rankings.
Remember, Sunny scored that in the 4th innings on English wickets chasing a 400+ total
There have been only 6 players in the entire history of cricket who have scored a double hundred in the 4th innings. Sunny’s score is 2 runs behind George Headley and 1 run behind Nathan Astle.
And remember this…
Gordon Greenidge, one of the 6 to have scored a double in the 4th innings, scored 214* against England in 1984 and WI won and that put Greenidge’s innings in the Wisden rankings 21 of the greatest Test innings of all time. Sunny’s innings is 74th on the list but not top 10. The only Indian batsman on the top 10 is VVS Laxman for his 281 in 2001.
The difference between Greenidge & VVS Laxman and Sunny is the result. Had India won, Sunny ‘s innings would be in the top 5 greatest innings of all time ( Laxman’s innings is in the 6th spot) above Greenidge’s 21st spot and above Laxman. Wisden rankings are weighted on the results.
Greenidge’s innings chased a total of under 350. Sunny’s score chased 438 and ended up 9 runs short for a draw.
So yes, without a shadow of doubt, that is the greatest innings played by an Indian batsman outside India. The only other innings that rises to that calibre is Laxman’s innings but his was in Kolkata not at the Kennington Oval.