In the “romantic” old days of the Indian Railways, the most important trains in each jurisdiction had low numbers-and often the most important trains were the pair 1 and 2 which were invariably Mail trains. We take a look back to the year 1976 (when the system was quite similar to today’s, except that the number of zones was less) and see what happened to the trains numbered 1 and 2 then. Some are still important (if not the most important trains on their route) while others have become quite unimportant.
These were: 1/2 Bombay VT/Howrah Mails via Nagpur (also called the Calcutta Mails via Nagpur) 1/2 Howrah/Kalka Mails via Delhi 1/2 Lucknow/Gauhati Avadh Tirhut Mails (metre gauge) 1/2 Madras/Mangalore Mails 1/2 Guntur/Secunderabad Golconda Expresses 1/2 Bombay Central/Ahmedabad Gujarat Mails 1/2 Ahmedabad/Delhi Mails (though renumbered 201/202 between Rewari and Delhi), metre gauge and even 1/2 Gondia/Jabalpur Expresses on the narrow gauge. We can see that all of these trains had been around for a long time (probably since the 19th century) except for the Golconda Express which was started by the new South Central Railway in the late 1960s. Over the years cities and stations were renamed, the train numbering changed to four digits for most long-distance trains around 1990 and then to 5 digits for all trains in 2010. To begin with, we look at the 1/2 Bombay/Howrah Mails as they were in 1976:
At that time this was the top train on this route as the Geetanjali Express was yet to start. It had the classical Mail timings of the olden days, leaving at night and reaching in the early morning (though in this case there was an intervening day). In 2014, this pair of trains has the rather uninteresting numbers 12809/12810. Those more familiar with the railways can deduce that this pair of trains are superfast (for what it is worth) and “belong” to the South Eastern Railway. The timings then and now:

The entire route is electrified now (about half was electrified in 1976) and timings have come down by about 2 hours. There are other faster trains on the route such as the Geetanjali and Duronto, but the Mail is still considered prestigious by the older generation-particularly in the eastern part of the country.
Now for the 1/2 Howrah/Kalka Mails:
At that time the Rajdhani had been running for several years but was still considered to be too extravagant for most travellers. The Poorva Expresses (often called the AC or Deluxe) were gradually becoming popular. The entire route between Delhi and Howrah was electrified around this time. By 2014, the 1/2 Mails had become 12311/12312, meaning that they were superfast and run by the Eastern Railway. These were the timings:

As we can see, they take almost exactly the same time between Delhi and Howrah. In the mean time there are two Rajdhanis daily which have attracted the upmarket travellers besides two Durontos. So the Kalka Mail has moved down the pecking order although, as in the previous case, the older travellers from eastern India still have high regard for the trains.
On the metre gauge, one of the longest hauls was on the 1/2 Avadh Tirhut Mails between Lucknow (LJN) and Guwahati. Even in the late 70s, there was no broad gauge link from Northern India to the North-East. So this Mail and its poor cousin the 15/16 Lucknow/Guwahati Express were the only links on this route. There was also the Assam Mail which ran on the broad gauge from New Delhi to Barauni, which connected with the metre gauge Mail all the way to Dibrugarh Town.
But over the years it lost its prestige with the coming of the broad gauge on the NER and NFR. By the 90s it became the Avadh Assam Express (demoted from Mail status) was running on BG on practically the same route up to New Jalpaiguri. It was then extended westwards to Delhi and finally to Lalgarh near Bikaner. Eastward it was extended to New Tinsukia. Worse still, it was not even a superfast but merely the 15909/15910 Avadh Assam Express. The 37-hour run between Lucknow and Guwahati (formerly Gauhati) had been reduced to 33 hours. Otherwise, time had not been kind to this train as it was involved in one of India’s worst rail accidents in 1999. (At that time it was running between Delhi and Guwahati). Here is the timetable of the old Mail and of its extended run in 2014. Note that it reaches its destination on the 4th day and has one of the longest runs of any passenger service in India.

To conclude this section we have the 1/2 Madras/Mangalore Mail. I am not sure how old it is as the timetables of the 1930s and 40s show only the Malabar Express on this route. By the 1960s the Mail appeared in its present form. Later the Malabar Express started running from Cochin (and still later further south from Trivandrum) to Mangalore while the 1/2 Mail got a companion West Coast Express by the mid-60s.
Here are the timings in 1976 and of its avatar of 2014, when it had become the 12601/12602 Chennai/Mangaluru Mail (fortunately still superfast) with these timings:

Here the 18-hour run has been reduced to 16 hours although a fair portion of the route is not electrified.
We will take up a few more “number ones” in the next section, which would be up on Aug 11.