From the Stowe 1848 Sale calalogue:

The Chapel is adorned with carvings, and wainscoted through with cedar, which latter was taken out of a Spanish prize ship bound to the Havannah, and brought into Padstow, Cornwall. It was there purchased by John Earl Granville, who was then building a magnificent mansion at a place called Stowe, near Kilkhampton in that county. Lord Cobham bought it out of the wreck of that edifice, and having conveyed it round London by water, appropriated it to the fitting-up of this Chapel, which he was then building. The cedar was worked by Michael Chuke, and the carvings are by Gibbons. The ceiling of this chapel is after the design of that in the Chapel Royal, St James’s. Within the rails of the Communion-table, hang the Colours of the First Battalion of Militia, which, under the command of the late Duke of Buckingham, volunteered for foreign service, and joined the British Army in France, under the Duke (then Marquis) of Wellington. As a tribute due to the Officers and Men who followed him on this service, the late Duke of Buckingham placed, on one side of the door of the gallery, the following inscription, on a marble tablet:—

The colours which hang in this Chapel, belonged to the First Provisional Battalion of Militia, composed entirely of Volunteers from the English Militia. This regiment, under the command of Richard Marquis of Buckingham, joined the British Army in France, under Arthur, Marquis of Wellington, in the Year MDCCCXIV.

In remembrance of the Officers and Men who accompanied him upon this service, and assisted in setting an example to their Countrymen, Richard Marquis of Buckingham preserved these Colours, which he recommends to the care of his descendents.

On the other side of the door, on a corresponding marble tablet, are inscribed the names of the Officers and Staff of the Regiment, together with a return of the Quotas of the different Regiments of Militia which formed the battalion. These colours were not sold during the recent sale; but the altar-piece, and a very curious antique shrine, brought from Antwerp by the late Thomas Astle, Esq., shared the general wreck. The banner of the present Duke of Buckingham, as a Knight of the Garter, is also preserved here. It should be mentioned, that up to the period of the death of the late Duke of Buckingham, Divine Service was regularly performed every morning in the Chapel at half-past nine, by one of the Duke’s chaplains; and her Grace invariably gave the good example of her household of a constant and punctual attendance.