Samuel Tanner was born in County Clare in Ireland in 1855, the son of an English-born railwayman named Edward Tanner. In 1871 he was a Railway Clerk living with his parents in Oswestry, probably working for the Cambrian Railway. In 1878 he married Annie Isabella Moodie of Pembroke and in 1879 he was living in Pembroke with her and daughter, Ellen. In 1880, aged 25, he took up a position of Traffic Manager with the Manchester & Milford Railway, moving to Aberystwyth. He appears to have been appointed by J. C. Russell in August, the same month as he became Manager under the Chancery Court, to replace Smedley, his predecessor, who he had dismissed. Russell also dismissed Wood, the engineer, reappointing James Weeks Szlumper CE who the Directors had sacked the previous year. The Company already had a Receiver but in December the Court of Appeal removed him and appointed Russell in his place. Meanwhile a battle started between Russell and the Directors over who controlled the management and over economies Russell wanted to make.  Tanner would have met Szlumper at this time. In October 1884, after 4 years with the M & M, Tanner accepted the position of assistant traffic Manager at the Buenos Ayres Great Southern Railway in Argentina at £700 pa, but returned after 18 months due to his wife's health. Judging by the birthplace of a son born in 1889 he returned to Llanfair, Montgomeryshire.
Tanner moved to the North Wales Narrow Gauge Railways, in the August 1890, aged 35, as secretary and traffic manager, signing the rolling stock certificates as Loco. Superintendent, at a Salary of £130 pa, succeeding R H Livesey who had left for Ireland in August.  J.W. Szlumper, signed the permanent way certificates as Engineer during Tanner's appointment.
Tanner remained at Dinas with the NWNGR until 1898, when he became Bankrupt, despite a £200 salary, with debts of £677, including Russell at £360, and assets of only £25. Russell felt obliged to terminate his engagement on 28 February as a result. By then, he and his wife had 8 children to support, and were living at Fern Villa, Llanwnda. He attributed his failure to sickness and a large family, but also admitted to living beyond his means. He appears to have been discharged the following Autumn on agreement to pay £25. The 1901 Census shows him as Book-keeper (Ships) in Bootle-cum-Linacre, West Derby, where he died in 1903, age 48. He features in two photographs which are illustrated in MacKay's ‘Light Railways’ published in 1896. The most significant shows him sitting in the then recently delivered carriage that was to become known as ‘The Gladstone Car’. This, together with a composite, hauled by ‘Moel Tryfan’, formed Gladstone's special from Dinas to Rhyd Ddu in September 1892. A report in the local paper  reads — 'At Dinas Junction, the headquarters of the NWNGR, Mr Tanner, the courteous manager of the company, had done his best in the way of decorations, and had provided a new saloon carriage for Mr Gladstone's journey to Rhyd-Ddu.'
It is interesting to note that the 1892 timetable bearing Tanner's name offered First, Second and Third Class travel on all trains, whereas the 1877 timetable, promoting an initial service to (Old) Cwellyn, offered only First and Third, with ‘Parliamentary’ tickets available on the earliest and latest trains to/from Cwellyn and Bryngwyn. This has since been explained by the fact that the Cleminsons did not arrive until 1878, because there was no second class accommodation until these coaches came. 
- J.S. Holden The Manchester and Milford Railway. Oakwood Press 1979 and contemporary newspapers
- Cambrian News September 26, 1890 North Wales Express August 15 1890
- North Wales Express of 16th September
- Welsh Highland Heritage, Issue 008
- Welsh Highland Heritage, Issue 023
- Michael Bishop "NWNG Carriages", Welsh Highland Heritage, Issue 040, page(s): 2-5