Grenfell had a fascinating life, though not quite so fascinating as he liked to make out. For the reality behind the myth (much generated by Grenfell himself) I´m quoting here from Colonel George St. Leger Grenfell: His Pre-Civil War Career by Stephen Starr (The Journal of Southern History, Vol. 30, No. 3 (Aug., 1964), pp. 278-297).
He was born in 1808, the son of a wealthy banker and metal trader, and after schooling in Holland he settled in Paris, where he married. So far, an unusual life maybe, but not an especially military one. During 1830 he saw action of a kind, joining friends in the street fighting in July that deposed Charles X and ushered in Louis Phillippe I, and for the next 5 years he was part of the National Guard, which in Paris in the 1830s functioned as a sort of riot police. His day job was as a banker in his father´s business, which by 1837 he had bankrupted, and in 1840 he fled France to escape charges of forging a commercial document. Rather surprisingly, by November 1840 he was in London and being made a Freeman of the Founders Company, his misdeeds forgotten, or at least indulged.
A somewhat romantic view of the 1830 revolution
What happened in the next three years, from 1840-1843 is a mystery. Grenfell himself claimed at various times that he was in the bodyguard of Emir Abd-el-Kader fighting the French in Algeria (of whom more anon), or with Garibaldi in South America though there is no evidence at all for the latter. The British consul in Montevideo was scrupulous in recording Britons with Garibaldi's forces and there's no mention of Grenfell there. At least by October 1843 he was in London, where he obtained a Dutch passport under the name of George St Leger, rather suspiciously given his past, and future, business arrangements.
By January 1844 Grenfell/ Leger was in Gibraltar, and shortly after in the Sultanate of Morocco, at Tangiers. He stayed there from 1844-46, partly clearing a stretch of wasteland he had bought, partly helping at the British consulate in Tangiers. Why a man of Grenfell's temperament and complete lack of agricultural education should chose to do either is not immediately obvious. Until you consider that smuggling between Gibraltar and Morocco was then a very lucrative, and not completely illegal, activity. Indeed in 1847 Grenville admitted leech smuggling, in association with another adventurer, "Count" St Marie, and his girlfriend (leeches were very important in medicine at the time, and Morocco was a major supplier). He was also a close acquaintance of a notorious Gibraltarian smuggler, Joseph Benjunes, and a Genoese with a very dubious past, a Sr. Mateos.
French troops in Algeria
Now, smuggling leeches is one thing, what brought Grenville to international attention was the much more lucrative trade of armaments. In Algeria, Emir Abd-el-Kader had been resisting French occupation with (mainly British) weapons smuggled in via Morocco, and given Grenfell's contacts, and his personal acquaintance with Emir Abd-el-Kader, it's not too hard to imagine that some of these weapons came via him.
Anyway, Emir Abd-el-Kader lost, but continued the fight from Morocco, resulting in July 1844 in a French squadron under the Prince of Joinville off Tangiers, and a bombardment of the city. Grenfell himself later claimed he commanded one of the batteries of the city, which were manned by Christian mercenaries, but that seems unlikely, and certainly no French vessels were seriously damaged as he claimed. In fact for the initial bombardment he wasn´t there at all, having been sent to Gibraltar to tell them what was going on, but he came back to a very dangerous city. Thousands of tribesman had flooded Tangiers, to defend and/or loot it, and Grenfell was a marked man, ironically being suspected of being a French spy, on the grounds that he had a French wife. He survived, but all the money he had invested in farming was lost.
The bombardment of Tangiers
Through 1845 and 46 Grenfell stayed working for the British consulate. His official work was mainly clerical, but he met Alexandre Dumas and went on a visit to Marrakesh, where it was he who presented Queen Victoria's gifts to the Sultan.
Exile and Gibraltar
Nonetheless, time seems to have weighed on Grenfell's hands, and his rash, but not very sensible, nature asserted itself. In March 1847 he and two friends went to visit Emir Abd-el-Kader in his Moroccan exile, as Abd-el-Kader had plans. He had decided that it would be in Algeria´s best interests (or at least in his) if he became Sultan of Morocco, which would require guns, and also British acquiescence. Grenfell was in a position to help with both and went to Lord Palmerstone in London to press Abd-el-Kader´s case.
Obviously none of this endeared him to the present ruler of Morocco, or to the French, and when the leech smuggling came to light it made a good case for his expulsion. As if that wasn´t enough Grenville then did about the only thing that would absolutely guarantee his removal from the country. Chasing a boy who had thrown a stone at him, Grenville followed him into a mosque. With his gun, and hunting dogs! The ensuing hysteria threatened not only him, but every other European in the city, and the British had no choice but to exile Grenville to Gibraltar.
And there he remained until 1854, sort of. He applied for a permit (refused) to visit Abd-el-Kader, with a Russian Prince, Demidoff and the notorious Benjunes, presumably to discuss business. And in 1853 he was joint partner with Mateos in the ship, Earl, although it is not clear for what purpose. He was to claim later that he was fighting Rif Moroccan pirates, and wrote a letter to the Times about just this subject. Given that Rif pirates would have been business competitors that may well be true. In 1855, Grenfell found himself serving in the Crimean War, he might, or might not, have been in the Indian Mutiny, and he was certainly in the Confederate Army in the Civil War, but those are other stories.