RailFans - we wander, but never get lost - Shaurya Kumar

Please read my earlier post carefully, sir. I didn't say that the North Bengal express existed before independence. I said that there was a train running between Calcutta and Sahibganj/Sakrigali after independence, which was sped up and introduced as North Bengal express after the cancellation of Darjeeling mail.
During the partition, cross border services did not operate for a long time. During this time (1947-48), the entire north east was cut off from Calcutta. So, passengers relied on the following chain of trains -
1) Calcutta (Howrah) to Sahibganj or Sakrigali ghat...
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by Broad gauge (by a passenger or the successor of the loop express)
2) Manihari ghat to Kishanganj by metre gauge.
3) Kishanganj to Siliguri by the narrow gauge DHR extension.
Even before partition, there was a Howrah-Kiul passenger (running since 1927 at least based on my EIR timetable of 1927) , and a loop express between Howrah and Danapur via the Sahibgunge loop that were used by passengers to get to Sakrigali ghat and cross the Ganga by ferry. These were running in 1943 ( you can see the timetable on the IRFCA site).
These passenger services were reorganized after independence so that people from Calcutta had access to North Bengal while the problems of the partition were sorted out. One of the reorganized services was sped up, converted into a fast train and branded as the 'North Bengal' express.