The Invertiel Junction was a reminder of the rivalry between the Caley and the NB. The coal owners of West Fife had long complained that their coal had to travel 25 or so miles via Thornton to get to Burntisland, only 6 miles away as the crow flies.
In 1895 the Kirkcaldy and District Railway, backed by the Caledonian, proposed to build a line from Larbert and Grangemouth, via a tunnel under the Forth at Kincardine, Dunfermline, and Auchtertool to a new harbour at Seafield, with a branch from Lochgelly, offering the coal owners of Cowdenbeath and West Fife a shorter and cheaper route to a port, and breaking the NBR monopoly in Fife.
Work was started on the port and on the railway leading to it, but the Act for the whole line was not granted, and the CR lost interest. Obviously they were more interested in taking coal West to Grangemouth than East to Seafield. Eventually in the early 1900's, to guard against possible future Caledonian invasions, the NBR built the line we now remember from near Cowdenbeath to Invertiel, with, of course, the junction leading towards Burntisland, the major coal port. However there were never more than two trains a day down this single line, (as compared to 35 - 40 via Thornton pre WW1) and most of the coal from West Fife continued to trundle round by Thornton.
In the post war period a drift mine was opened at Seafield and a branch was opened to it from the Auchtertool line, using the formation and earthworks of the abortive Kirkcaldy and District railway. I haven't been there recently, but some of the bridge parapets used to be visible at the side of the Kinghorn Road. A few years later, of course, everything was swallowed up under the new Seafield Pit, now itself lost under housing.
Allan F