For a country that ranks in the low 150s in international football, it is an anomaly. And yet it has become a cultural tradition that goes far beyond the boundaries of football or even sport. When East Bengal and Mohun Bagan clash in Kolkata, the snobby bhadralok undergoes a metamorphosis – once inside the stadium, the sort of abuses that emanate from his lips would put most people of kalchaar to shame.

Even if you aren't a football fan, several markers on derby day will let you know that the big clash is on hand. One of these are the long rows of tempos on the roads leading up to the Salt Lake Stadium. These tempos are filled with supporters of either side (East Bengal in red and gold, Mohun Bagan in maroon and green) who delight in taunting their rivals as they pass each other.

It was no different this past Saturday.

Once inside the stadium though, there was no mixing. On the day of the big clash, the stadium is always divided neatly into two halves: one half majorly dressed in maroon and the other in sparkling red and gold.

“It [the rivalry] is a cultural goes beyond just football,” said Amitava Sanyal, who is writing a history of the East Bengal football club and on the social history of football in Kolkata. “And it is based on two distinct identities...the Bangals (those who emigrated from present-day Bangladesh and support East Bengal) and the Ghotis (those who identify themselves as the original residents of West Bengal and support Mohun Bagan).“

Mohun Bagan had always been the most eminent pre-Independence football club but East Bengal emerged from the shadows in the 1920s, when a need to assert the Bangal identity was felt. Almost a hundred years from then, the support bases remain as strong as ever – one flag in the East Bengal colours proudly assert that they are “100% Bangal".

“The teams themselves always had a mixture of both Bangals and Ghotis,” reminded Sanyal. “But through the forties till 1971, as immigration continued in Kolkata, East Bengal’s support base became more and more entrenched. Many of the immigrants coming in at that time were desperate people, many well-educated but living in squalor. The club, East Bengal became one of the few rallying points in their lives.”

Back at the stadium on Saturday, both sets of supporters had watched the two teams play out an absorbing but scoreless first half. The first signs of frustration were building before finally the red and gold brigade had their moment of triumph, courtesy a lovely strike from their favourite striker Ranti Martins.

Jubilation rang out at one end while there was pin-drop silence at the other. Some took off their shirts and started waving them around. The moshall (flares made by setting fire to paper, a prominent aspect of the East Bengal logo) also made an appearance.

But it did not last long. Within 15 minutes, Mohun Bagan scored at the other end, this time from a free-kick. This time, it was the turn of the maroon and green to celebrate.

“Today's supporters are smart, “said Sanyal. “If you look at the attendances, then you will find that low-consequence matches are less-attended, maybe 20,000 people in the stadium. But when there is a big match, it can go up to 70,000 and more.”

As the first derby of the year in the I-League, this was overwhelmingly a big match. The stadium was packed. But as the much anticipated clash ultimately petered out to a 1-1 draw, both sets of supporters seemed confused with the result. “We played so well, we should have won,” lamented an East Bengal supporter to his friend. “But look at it this way, they [Mohun Bagan] are I-League champions. We did so well against them,” his friend replied. Suitably mollified, the supporter let out another roar of triumph before disappearing into the evening.

An uneasy truce then. Till the next derby comes along to divide the City of Joy.