I purchased this booklet a few years ago but I’ve only recently looked into the history of the author. It’s an excerpt from Volume L (50) of the “Transactions of The Cardiff Naturalists’ Society”.
It contains a report by John Stuart Corbett on the Society’s visit to Castell Coch on June 27th 1917. The booklet is only a few pages long but it’s a great little piece of history.
The Cardiff Naturalists’ Society was formed in 1867 and published annual Transactions from 1868 to 1986. Many of these documents have been digitised and are available on the National Library of Wales website.
The booklet was printed in 1920 by William Lewis (Printers) Limited. I’ve included the full text at the end of this article.

“We are in the Red Castle in the Red Forest; the name of the Castle, which it shares with several others in Wales, being no doubt derived from the colour of the local stone of which it was built, which, when the building was new, would have a distinctly red appearance. As to the Red Forest, by which name the wood in which the Castle stands was known in mediaeval times, it seems probable that it was derived from the autumnal colour of the beech trees, of which the wood largely consisted, in those days perhaps to a greater extent than at present.”
John Stuart Corbett – June 27th 1917
Cardiff Naturalists’ Society
The Cardiff Naturalists’ Society celebrated their 150th anniversary in 2017 and had an exhibition at the Cardiff Story Museum.
“In modern times it has been the premier place for people with a wide interest in all aspects of wildlife as it has the most varied programme of indoor lectures and field meetings on offer of any local society. Talks and field trips cover all aspects of wildlife from plants to animals, birds, the environment and geology. With a mix of talks on local places in and around Cardiff and also the wider world. They are suitable for all levels of knowledge.”
Cardiff Naturalists’ Society

John Stuart Corbett
John Stuart Corbett (16 May 1845 – 9 March 1921) was the Solicitor to Lord Bute from 1890 to 1917. This period covered the last ten years of the 3rd Marquess’ life and the remaining period for the 4th Marquess.
He was the president of the Archaeological section of the Society in 1900-1901. As a keen historian, his knowledge of the lordship of Glamorgan was unrivalled.
The Society featured a biography in Volume LVI (56) in 1923.

Castell Coch by John Stuart Corbett
The following is a copy of a short paper on Castell Coch read by Mr John Stuart Corbett, on the occasion of a visit of members of the Cardiff Naturalists’ Society to the castle, on June 27th, 1917.
I have been asked to say something to you as to the history of this Castle, and that is in one sense a simple, and in another a most difficult matter, for practically nothing is known of its history, and very little of its origin.
We are in the Red Castle in the Red Forest; the name of the Castle, which it shares with several others in Wales, being no doubt derived from the colour of the local stone of which it was built, which, when the building was new, would have a distinctly red appearance. As to the Red Forest, by which name the wood in which the Castle stands was known in mediaeval times, it seems probable that it was derived from the autumnal colour of the beech trees, of which the wood largely consisted, in those days perhaps to a greater extent than at present.
So far as I am aware, the Castle is not even mentioned in any document of a date near the time of its building, and this is curious, considering the numerous records (printed by the late Mr. Clark in his “Cartae”) which exist with respect to the disputes about the building of Caerphilly, and the fact that it is almost certain that Castell Coch must have been built about the same time, and by the same person, namely, Earl Gilbert de Clare, who ruled in Glamorgan from 1262 to 1295. Mr. Clark, in his “Mediaeval Military Architecture,” expresses the view that Castell Coch might be slightly earlier than Caerphilly, but the two must have been so near in point of date that it would hardly be possible to found any argument as to the order in which they were built from the style of the architecture. I here refer to the earlier portion of Caerphilly built by Gilbert de Clare. In his “Land of Morgan,” Mr. Clark regards it as certain that Castell Coch was the work of that Gilbert de Clare who built Caerphilly, and at a somewhat later date, Morlais.
That he must have been the builder, and the approximate date, can be proved with practical certainty from historical facts known to us.
The Lordship of Senghenydd, in which both Castell Coch and Caerphilly stand, was in the hands of Welsh Lords up to the time of the above-mentioned Gilbert de Clare.
An extent or inquisition of Glamorgan, taken soon after the death of his father, Earl Richard, in 1262, expressly mentions that Griffith ap Rees held Senghenydd at that time, owing no service but a heriot at death.
It was not until 1266 or early in 1267 that Gilbert, son of Richard, captured and imprisoned this Griffith, who was last Welsh Lord of Senghenydd, and seized the district into his own hands. Then followed the building of Caerphilly and the long controversy with Llewelyn, Prince of Wales, to which this gave rise, and which at last terminated by the death of Llewelyn and the conquest of North Wales by Edward I. This event, and the end which it put to the fear of invasion from the north down the Valley of the Taff, would much reduce the importance of Castell Coch, and may be the reason why no mention is made of it in the inquisitions on the deaths of Lords of Glamorgan, with one exception, the inquisition taken in 1307 on the death of Joan, Countess of Gloucester, where “Rubeum Castrum” is mentioned in a list of the “members” of Senghenydd. Practically all we know about its origin is that it was almost certainly built by Gilbert de Clare. It could not be earlier than his time, because he was the first Lord of Glamorgan to possess Senghenydd.
What happened to it afterwards, we do not know. There are legends, referred to by Mr. Clark in his “Mediaeval Military Architecture,” of its having been taken by the Welsh.
Such events might have happened in the great rising which took place in 1295, the last year of de Clare’s life, in the rising of Llewelyn Bren in 1315, or in the wars of Owen Glyndwr. In fact, there can scarcely be any doubt that if it was maintained as a fortress in Glyndwr’s time it would fall into his hands, as was the case with Caerphilly and Cardiff.
In his description of the Castle, as it was in its ruined condition before the recent restoration, Mr. Clark says that two-thirds of the circumference of the South tower had been blown away by a mine. If this is so, it followed that its destruction took place after gunpowder had come into use, though at what date we do not know. It seems to me not improbable that it may have been destroyed by Owen Glyndwr, like so many other Castles in the neighbourhood.
At any rate, it was in ruins in Leland’s time, for he writes thus:-
“Castelle Gogh standeth on a high Rok of a redde stone
“or Soile a 2 Miles from Landaf upper on Taue; a
“quarter of a mile from the Est Ripe of Taue
“Castelle Gough al in Ruine no bigge thing but high.
“It longith to the King and standeth by ‘Keuen On.'”
Rhys Myryke says of the Castle that it was supposed to be built by Ivor Bach, which is of course quite impossible as regards the Castle with which we are dealing.
If in fact Ivor had any fortress hereabouts, it must have been some previous building either on or near the site of the present Castle, or else perhaps what Mr. Clark calls “the Cymric Camp” higher up. What exactly that camp was I do not know. It is marked on the Ordnance Map as remains of an entrenchment, but I am not aware whether it has ever been carefully examined.
Ivor Bach was Lord of Senghenydd and ancestor of that Griffith ap Rhys who was dispossessed by de Clare, and it may well be true that he had some stronghold at or near the site of the Castle. Of that, however, nothing is certainly known. What no doubt is true is that he surprised Cardiff Castle in or about 1158 and took William, Earl of Gloucester, prisoner, carrying him off to some fastness in the hills, which may or may not have been near this place.
Mr. Clark in his work to which I have referred gives a very careful and minute description of the ruins as they stood before reconstruction, so far as he was able to investigate them, which he describes as being a matter of some difficulty, owing to the extent to which they were overgrown with brushwood. I may add that in a paragraph at the end of his notice, added after the rebuilding, Mr. Clark says the restoration is very complete and in strict accordance with what has been ascertained of the original structure.