Tomlinson 1915

The official history of the North Eastern Railway, Its Rise & Development, was written by the eminent historian William Weaver Tomlinson in 1915.   David & Charles published an edition of the 800+ page book in 1967 which may be available second hand for about £40; there is also a 2015 edition from Andesite Press.   However, the first edition is freely available on line, including as a pdf download of 110 MB, with the further advantages of being much lighter and machine searchable.

Tanfield Gradient Profile - Tomlinson p343

Redheugh Station at the quayside end of the Tanfield Branch - Tomlinson p309

The book contains several portraits - TE Harrison
 on p514 featured on this blog on 21 April 

Download the book from the University of California:
https://archive.org/details/northeasternrail00tomlrich/mode/2up 

To search the pdf, use CTRL-F & have patience - it's a very large book.