Definition of "vanquisher"

HSTs continued to provide sterling service during these years, so much so that when Virgin and Midland Mainline brought their new wave of high-speed diesel electric multiple units [...] on stream, many preferred the ride and comfort of the vanquished to the ride and comfort of the vanquisher.

2021 October 6, Greg Morse, “A need for speed and the drive for 125”, in RAIL, page 53