The locomotive that pulled Queen Victoria's first train journey in 1842 was Phlegethon. The journey took place on 13 June 1842 on the Great Western Railway, making Victoria the first reigning British monarch to travel by train.
Victoria travelled in a special royal saloon built by the Great Western Railway. The train carried her from Slough to London Paddington, completing the journey in an age when railways were still a striking new technology. Daniel Gooch drove the locomotive, assisted by the railway's chief engineer, Isambard Kingdom Brunel.
Phlegethon belonged to the GWR's Firefly class and was built in 1842 by Fenton, Murray and Jackson. Its name came from Greek mythology: the Phlegethon was one of the rivers of the underworld, associated with fire.
A frequent confusion concerns Queen Adelaide, who travelled by train earlier, in 1840. She was the first member of the British royal family to do so, but Victoria was the first British monarch. That distinction is why the 1842 journey is especially remembered.