Some notes about sources
I have researched many newspapers and learned that journalists have a reputation for not letting accuracy get in the way of a good story so I was intrigued to see a recent book about construction of the GCLE which presented newspapers as a valuable resource.
Alas, newspaper reports are stuffed with errors and faulty interpretation and while I have gone through this book and its many errors I have not reviewed it because there simply isn't the space to set right so much misinformation. One of the problems is that the author writes about engineering aspects of railway design and construction but is poorly qualified and cannot spot the codswallop published by newspaper journalists. Instead, here is an example from a newspaper, via an old fashioned Xerox, in which the GCLE route was described and I have highlighted in yellow a litany of errors, some of them impossible to see how they could have been derived. That in plain English is fabrication:

(Click on the image for an enlargement)
This account was actually part of an article in the Morning Post (a London publication which later became part of the Daily Telegraph) and this part was repeated by the Northampton Mercury with emphasis on the line where it passed by locally. All the local papers followed construction and then opening. Here are some observations on the yellow-shaded content:
"on past Sulgrave to Helmdon" - oops! It's actually the other way round.
"viaducts built of blue brick" - nope, common bricks faced with brindles.
"[at Brackley] 22 segmental arches " - actually 20 arches and 2 steel spans.
"another at Banbury" - no there isn't and I have no idea where this has come from.
"at Culworth station a junction is made for the line to Stratford-on-Avon" - no junction at Culworth station, the two junctions for Stratford were at Woodford & Hinton.
"Catesby tunnel 2,860 yards long" - actually almost exactly 3,000 yards long.
"three viaducts, one at Staverton with 11 arches and another at Willoughby with 13 arches" - they were: Catesby Viaduct (9 arches); Staverton Viaduct (8 arches) over the River Leam; and Willoughby Viaduct as described.
"immediately south of their station" - not immediately and to the north of the station.
Here are some illustrations:

This is the first viaduct misrepresented by the newspaper, at Brackley, which wasn't too far from Northampton and could have been visited by the Northampton & Banbury Railway which had a station in Brackley (that later became part of the SMJ). There were also local photographers in Brackley and Buckingham selling photographs as construction proceeded. The 20 "segmental arches" are clearly visible and the 2 steel spans at the south end. One of the arches was filled in. This photo was taken in the 1960s. I shall be writing up this viaduct and some of the others in due course. Photo: author's collection.
Click on the image for an enlargement
There were three viaducts north of Catesby tunnel.

Proceeding in the same direction as the newspaper, the first viaduct after Catesby Tunnel to be misdescribed was Catesby Viaduct seen here in the 1960s with 9 arches and a train headed by a Black Five passing by. Photo: Mervyn Leah.
Click on the image for an enlargement

The second was Staverton Viaduct with its 8 arches. The signal box was a short distance away on the left. Photo c1953: G.W. Goslin.
Click on the image for an enlargement
Newspapers can contain useful material but we all know the joke "I read it in the newspaper" and ten errors in two column inches beggars belief and illustrates how unreliable journalistic information can be and why it has to be treated with care. Otherwise pure baloney gets trotted out as "fact"; other authors plagiarise it; and as the saying goes, fiction becomes fact. I recall researching a particular GCLE episode (that Dow has glossed over) and all the local papers had covered - but the differences between them were so great and contradictory that I tore up my account! It's fair to say that the GCLE has not had a good press.
If I may conclude on a more positive note, this article states that Catesby Tunnel "saved a further climb of 120ft or so" - which can be seen by looking at the 6" map and its contour lines and is one of several reasons why the notion spread by modern authors that the tunnel "was planned to be a cutting" is codswallop.