In the memory of East Bengal Fans this day stands out - 29th September 1975. It was the IFA Shield Finals when East Bengal Club defeated Mohun Bagan 5-0 on the Mohun Bagan home ground. List of scorers in the order of the scores were - Surajit Sengupta, Shyam Thapa, Ranjit Mukherjee, Shyam Thapa, Subhankar Sanyal. Till date fans clamor for a repeat but it stands as an unbeaten record. It is the Highest Record Margin of victory in the clash of the two arch rivals.
If 60s belonged to Bagan, the next decade was unquestionably dominated by East Bengal. In first half of the 70′s, East Bengal won every trophy in India with remarkable ease. Most importantly, they didn’t lose a single derby match between 1969 and 1975 – for a period of 1932 days. The pinnacle of this run came on 1st October 1975 in Shield Final. Coached by P.K Banerjee, East Bengal were on the verge of a unique record of winning Shield for four back to back seasons.Three of the goals East Bengal scored were due to errors made by rookie ‘keeper Bhaskar Ganguly.
Surajit Sengupta started the rout, waltzing past two Bagan defenders to score the opening goal after five minutes. Six minutes later, East Bengal were awarded a penalty kick when Shyam Thapa was fouled inside the box by Tapan Basu. Thapa hit his penalty wide of the goal, as East Bengal failed to increase the lead. In the 24th minute, Subhas Bhowmik’s cross was spilled by Ganguly, and Shyam Thapa made amends for his previous error to make it 2-0. Ranjit Mukherjee’s goal in the 38th minute was perhaps best of the match. The goal resulted after a swift interchange of passes between Sengupta, Thapa amd Bhowmik. Mukherjee outfoxed Bagan stopper Nimai Goswami and took an unstoppable shot to make it 3-0. Shyam Thapa scored his second goal in the 51st minute. Bhaskar Ganguly again spilled a shot from Surajit Sengupta, and Thapa tapped the ball into an open net. Ganguly was replaced by Prashanta Mitra after the fourth goal, but the latter couldn’t prevent the Red and Golds from scoring their fifth goal of the match. Subhankar Sanyal made it 5-0 in the 84th minute.
East Bengal not only created a record of Shield wins; they also made the record (still unbroken) of the biggest victory margin in a derby match. The aftermath of this result was far-reaching. Bagan fans surrounded the club tent, setting some trees on fire; the players were afraid to go out. Subrata Bhattacharya and Prasun Banerjee somehow escaped and spent the night on a boat on the Ganges, before being rescued by Sailen Manna. For Prasun, this loss was ironic, as it came against a team coached by his elder brother. Mohun Bagan supporter Umakanta Paladhi committed suicide after seeing his beloved team slump to such a loss. In his suicide note, he wrote that in his next birth he wanted to be born as a Mohun Bagan player and exact revenge for this defeat. Curiously, Bhaskar would later become one of the finest goal-keepers in Indian football. Bijoy Dikpati and Nimai Goswami, the two Bagan centre-backs, effectively played their last match in the Green and Maroon jersey.After the fourth goal was scored, one East Bengal supporter had a heart-attack out of sheer ecstasy and had to be taken to hospital. Another Mohun Bagan supporter, Umakanto Palodhi, commited suicide that night. The suicide note he left reveals : "By becoming a better Mohun Bagan footballer, I wish to take revenge of this defeat in my next birth."
Source : http://www.thehardtackle.com/2011/high-five-memorable-kolkata-derbies/