Had it not been for the diligent attentions of his tutor, Lord Charlemont might have left no legacy other than a collection of empty wine bottles. In later life, the earl wrote of the entertainments provided by other members of the Irish gentry. "After dinner, the doors shall be locked, the keys laid on the table" and guests drenched in drink - which out of "pure Hospitality and Friendship is poured down their Throats" - until they could hold no more. The adolescent Charlemont, who had lost his father at the age of six, seemed destined to emulate his peers especially when he abandoned academic studies and took to keeping company with Jack St Leger, the erratic cousin of Lord Doneraile. However, it was at this moment that his tutor Edward Murphy, together with his stepfather Thomas Adderley, decided to save their charge by sending him on a Grand Tour. Charlemont was by no means unique in spending several years away from home - among his fellow Grand Tourists were Joseph Leeson, first Earl of Milltown, with his son Joseph jnr and his nephew Joseph Henry, as well as Ralph Howard, first Viscount Wicklow. For all of them, these travels served a dual purpose: the opportunity for a broader liberal education than that available at home (as proposed by Lord Chesterfield in the sequence of letters he wrote to his illegitimate son Philip Stanhope) and the acquisition of art works to be brought back home at journey's end. But Charlemont's tour was unusual in being longer than most - he was out of Ireland for eight years - as well as more extensive.
In addition to spending the customary time in Italy, he also ventured to Turkey, Greece and Egypt. Much given to measuring the dimensions of buildings encountered, he also succeeded in identifying the site of the ancient Greek city Halicarnassus. Charlemont was no different to any other Grand Tourist of the period in regarding classical culture as a lost ideal but he came to be caught uncomfortably in the mid-18th century debate over the respective merits of Roman and Greek art.
Rather like Chesterfield's dispute with Dr Johnson over the former's patronage of the latter's dictionary, so Charlemont almost contemporaneously became unpleasantly embroiled with Piranesi, who originally dedicated his Antichita Romane to the earl in the expectation of receiving financial assistance for doing so. This was not the only controversy in which Charlemont allowed himself to become embroiled. Their origins usually lay in his ambitions exceeding available income because, although he was certainly the equal in learning of such other great 18th century aristocratic patrons as the Earl of Burlington, the funds available to him were somewhat smaller.
So the Marino Casino - the most famous and best-surviving of all his architectural undertakings - appears to have taken decades to complete and may not have been internally finished even at his death. Similarly, the walls and ceilings of the principal floor in Charlemont House were reported as still unplastered in 1797.
Equally surprising in the late 20th century is the eclecticism of the earl's taste, since he has come to be considered an ardent proponent of neo-classicism through his work with the architect Sir William Chambers. In fact, until its transformation into Dublin's Municipal Gallery in 1929, Charlemont House contained instances of pure rococo decoration while the Marino property included an early example of Gothic design, perhaps inspired by the earl's friendship with Horace Walpole. In part because of Charlemont's profligacy, much of what he created has been lost; almost immediately after his death, financial retrenchment began, but in addition there was a serious fire at Marino in the early 19th century and the family seat, Roxborough, Co Tyrone - rebuilt by the third earl in the style of a lavish Victorian seaside hotel - was burnt down in 1922. Two hundred years after his death, the first Earl of Charlemont and his work are being subjected to scrutiny once again. This new biography pays particular attention to the years of his Grand Tour with the effect of unbalancing the book since only the last third covers the decades following his return to Ireland. In this section, Cynthia O'Connor concentrates almost exclusively on the earl's cultural interests, so that his involvement in Irish politics during the second half of the 18th century must be consigned to a single chapter.
It might have been wiser to have ignored this element of Charlemont's life altogether, because, fascinating as is O'Connor's book, the approach adopted will leave a reader feeling the need for a fuller biography.
Robert O'Byrne is an Irish Times journalist