The 2010 Asian Games gold-medallist and former national record holder in 3000m steeplechase, Sudha, went neck and neck with her Rio Olympics-bound Railway colleagues Lalita Babar and OP Jaisha till the midway mark.
But she broke away in the last two kilometres to cross the finish line with a record 1 hour 27 minutes and 31 seconds.
Sudha got richer by Rs 3 lakh which included a bonus Rs 50,000 for breaking the course record in the Rs 22.80 lakh prize money event.
Sudha, who had finished second behind Kavita last year, made her previous experience count as Lalita (1:27:47) and national marathon record holder Jaisha (1:28:05) battled the pot-holed Kolkata roads laced with 'tram tracks' to finish second and third respectively.
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In the men's elite section, Elam Singh finished with a timing of 1:20:14, while Srinu Bugatha (1:20:16) and O Sanaton Singh (1:20:23) were second and third respectively.
Trained under the Belorussian middle and long distance coach Nikolai Snesarev in the national camp in Ooty, the trio had been running together for a long time.