He was the third son of Robert Nicholas, Esquire, at one time Member of Parliament for Cricklade, and many years chairman of the board of excise, by Charlotte, sixth daughter of Admiral Sir Thomas Frankland, Baronet.

[3] Nicholas was schooled at Mr. Newcome's establishment at Hackney, and was admitted, upon the nomination of the Marquess Cornwallis, a cadet of the Royal Military Academy, Woolwich at the end of 1799.

[2] After completing the usual course of instruction at Chatham he was employed on the defences of Dover, during the formation of the great works upon the Western Heights, between 1801 and 1805.

[4] He describes it in a letter from Monteleone in Calabria, 11 July 1806: I had the most narrow escape of any; a cannon-ball carried away my large boat-cloak and pad, which was strapped on behind my saddle, which by the shock was thrown on one side; and my horse, rearing and plunging, threw me on the ground; however no accident happened but the loss of my cloak.

A few inches more must have carried away the whole of my hind quarters; but the shot (of small calibre) passing through the cloak, which was very large, and lined with green baize, lost its effect in going by me.

[10] In the general retreat towards the sea and Alexandria, Nicholas notes how those left behind were "barbarously butchered by the Turks, whose cavalry came out and deliberately cut off the heads of our poor helpless comrades.

[9] He writes, "We made batteries innumerable; but the difficulty of bringing shot and shells from Alexandria prevented our keeping up so hot a fire as we could wish.

We continued in this position before the town from March 22nd to April 21st, the Turks making sorties and annoying us with shot and shell daily during the whole time.

[13] Nicholas was seriously ill on leaving Alexandria, from an injury received on his left breast by jumping into shallow water head first and striking upon a hidden rock.

His breathing and lungs were affected, and his surgeon, Mr. Fitzpatrick, who had attended him for nearly three years, dreaded a rapid decline, as he could not raise his voice above a low whisper, and was so weak that the least irritation threw him into fits.

In that despatch, Colonel Robertson, in describing the obstacles which the British opposed to the French by cutting across the paths leading to the heights of Milia down to Scylla, writes, "This work, as well as the levelling fences, &c. proceeded rapidly and effectually under the direction of Captain Nicholas.

[7][16][17] For this action he was again favourably mentioned in the letter of service to General Sherbrooke, on which he observes, my staff position gives me those opportunities, which otherwise would not offer themselves was I doing the duty only of my own immediate profession.

The life of a Bond-street Buck, or a country Sportsman, would, I suspect, little suit my habits, formed as they have been to military activity, and constant employment; … I have always been seeking credit and reputation; and when I shall be debarred of such pursuits, I know not … to what I could for a constancy turn my thoughts.

[18]He made a tour of the principal towns, and the country in the western part of, Sicily, and his report was forwarded by General Sherbrooke to the secretary of state for the war department.

[7] At the very close of the defence, Major Charles Lefebure, the commanding Royal Engineer, had his head taken off by a round shot whilst inspecting the enemy's works from over the crest of the parapet.

Poor Lefebure was the last man in Fort Matagorda, and was in the act of preparing the mine to blow up what remained of it, when a cannon shot struck his chest.15 June.

[20]At La Isla, in October 1810, Nicholas received an order to take charge of the Engineer department during the absence of Captain Birch, who had gone to Cadiz to recover his health.

[22] In March 1811, he took part in the Battle of Barrosa, and with Captain Birch was publicly thanked on the battlefield by Graham, who, holding out his hands to them, said: "There are no two officers in the army to whom I am more indebted than to you two; you have shown yourselves as fine fellows in the field as at your redoubts.

On the night before the siege of 6 April 1812, having volunteered to reconnoitre, he stripped, and crossed the artificial lake to the east of Badajoz, known as the inundation,[23] and ascertained the safest passage for the column.

[26] Then, on seeing Lieutenant-colonel Macleod and Captain James fall,[27] and hearing the soldiers ask who was to lead them,[7] he led a third onset with some seventy men,[24] ordering two of them to carry him up the breach.

Fitzpatrick first applied himself to elevate the ribs, to assist his breathing; and on the third day after the siege Nicholas was moved from his tent into Badajoz, where he was able to write a letter to his father, dated 7 April.

[34][35] In around 1814 the enamel painter Henry Bone also made a pen and ink drawing, after Pymm's original, which is now in the National Portrait Gallery, London.