George Pretyman-Tomline, the Bishop of Lincoln, was Pitt's tutor at Pembroke Hall in Cambridge, one-time private secretary, and a life-long friend. He was at Pitt's house at Putney Heath when Pitt died, and by Pitt's personal request he became one of Pitt's executors at his decease along with Pitt's brother Lord Chatham. Tomline had a close connection to the Minister from the time Pitt was fourteen years old, and he was certainly one of the select few who were privy to Pitt's private life. Due to this personal relationship with such an illustrious statesman, it is no wonder Tomline wanted to write about Pitt's life. Indeed, within six weeks of Pitt's death, Tomline announced he would write his biography.  Other friends of Pitt who contemplated writing Pitt's biography at different points in time were George Rose, Charles Long, and William Wilberforce. Unfortunately for the world, nothing came of those intentions. Lord Lowther named a Mr. Stonard, a private tutor residing at Chertsey, to write something, and Lady Hester Stanhope apparently approved of the choice, but that too fell through.  Tomline was left to get on with the task of writing Pitt's life.
Needless to say, some of Pitt's other friends had their reservations. Lord Mulgrave expressed his “doubt of the Bishop giving to the work the necessary brilliancy and animation of style which should distinguish the biography of so illustrious a character, a striking feature of which was that splendour of language which should at least not be neglected in describing him [Pitt]. It is highly important that there should be something in the manner of telling the facts which may keep alive to a late period the desire and pleasure of perusing them.” 
Lord Camden also did “not seem to entertain any hope of a very spirited history from that quarter.”  George Rose desired to write in conjunction with Tomline, but Tomline was determined to write it alone.
Sadly, many of Pitt's personal papers have been lost or destroyed, unintentionally or otherwise. For instance, the widow of Edward Wilson, Pitt's childhood tutor, was said to have had "papers of a very interesting nature indeed, and of great extent."  Henry Dundas, Lord Melville once commented that he had masses of information in his head and all unwritten. The same would have been the case with Wilberforce and Long. Piecing together Pitt's life outside the walls of Parliament would have been tricky even then as it is now. By and large, Pitt lived a life of relative seclusion, admitting very few into his inner circle of friends. Most of those were politicians themselves. The little tantalising glimpses we are afforded offer us minute snapshots of a life dedicated to the service of his country. They also leave us wanting to know more about Pitt the man.
According to Lord Rosebery, Tomline's biography of Pitt fell very short of the mark. Rosebery thought that "there is no drearier book in all biography. The Annual Register, on which it appears to be modelled, is by comparison sparkling and vivid.”  Just for the record, that isn't saying very much. To assert that Tomline is Pitt's much-maligned biographer is putting it extremely mildly, and is a gross understatement. Given his intimate and detailed personal knowledge of Pitt himself, much more was expected, but what must be taken into account is that Tomline was writing and publishing at a time when most of Pitt's friends - and opponents - were still living. Pitt died relatively young, at only 46, and some of his friends, like Lord Sidmouth (Henry Addington), lived to a very advanced age. Indeed, many of them outlived Tomlime. Therefore, he was justified in being concerned about the impact of putting into print recollections of events which were at that time still very much within living memory. In short, he held back a great deal. One of those things was his projected fourth and final of his Memoirs of the Life of the Right Honourable William Pitt. The first two volumes were published in 1821, and were reprinted with the addition of the third volume in 1822. Portions of the final, unpublished volume are now held at the British Library under Add Ms 45107-45108, and are arranged in thirty quarto notebooks.
I had a look at the portions under Add Ms 45107, and especially Chapter XXVII as it relates predominantly to Pitt's private life. Below are some of the gleanings I gathered from what Tomline has to say in that chapter; for further follow-up, it was also reprinted in The Monthly Review (Vol. 12: 1903). All quotes are from Tomline:
Pitt's first attack of gout was in 1789 when he was 30. Pitt's friends started noticing a change in Pitt's health as early as 1793, but the physician Sir Walter Farquhar wasn't brought in until 1795. Tomline noticed a gradual decline in Pitt's health, and in September 1802 Pitt was "seized at Walmer Castle with a most violent illness of a bilious nature, and his life was for some hours in imminent danger." Following that attack, Pitt went to Bath at the end of October 1802, and did not resume attendance in Parliament until May 1803. Between October and November 1805, Pitt suffered from his worst attack yet, and he went again to Bath in early December. He had two attacks of gout there. Tomline says "his [Pitt's] person became suddenly emaciated, his strength was greatly reduced, his appetite entirely failed, his countenance was totally changed, his eyes were lifeless, and his voice was hollow." There was a huge change observed between early December 1805 and early January 1806 when Pitt returned to his house at Putney Heath. From that point, the decline was rapid. Tomline was at Putney with Pitt from January 12th until Pitt's death. On the 22 January, the day before Pitt died, Tomline was finally able to acquaint him with his imminent death (although Pitt must have been aware that he was dying), and to pray with him and settle his affairs.
Tomline remembered that “after the prayers were finished, but while I was still kneeling and unable to restrain my feelings, which he [Pitt] observed, he took hold of my hand, and in a manner and in a tone of voice which are indelibly impressed upon my mind, said to me, “I cannot sufficiently thank you for all your kindness to me throughout life.” I was too much overpowered to make any reply. Luctus leves loquuntur, ingentes stupent." By that quote from Seneca, Tomline meant that slight losses can be expressed, but great griefs are speechless. The imminent loss of Pitt was afflicting for Tomline. On such occasions there are no words strong enough to express such emotions.
Tomline admits that Pitt refused the Sacrament twice, saying he was too tired and wanted to rest a while. Unfortunately, Tomline had no opportunity after the morning of the 22 January to administer the Sacrament, and Pitt's “soul departed in a gentle sigh at a quarter past four on Thursday morning.”
On a lighter, anecdotal note, Tomline alludes to Pitt's extraordinary powers to set aside the pressing cares of the day, and fall into a rapid, profound repose. The occasion Tomline refers to relates to an instance from the beginning of Pitt's first time as Minister:
“The scrutiny after the Westminster election was among the most vexatious and harassing occurrences in the whole course of his administration; and in the morning, after one of the perplexing debates and unfavourable divisions on the subject, in 1785, the outline and result of which I had learnt, I went to Mr. Pitt’s house, anxious to hear the particulars from himself. I accidentally met his valet in the hall, and asked him whether Mr Pitt was up, and he said, “No.” I then asked at what time he had ordered himself to be called, and the answer was that he had not ordered himself to be called at all; upon hearing which, I said, perhaps with a little impatience, “But why did you not ask Mr Pitt at what time he wished to be called?” The answer was, “I did, sir, but the moment my master’s head was upon the pillow he was fast asleep.”
Another great description of Pitt's sweet, mild nature in private society is this one:
“…of the amiableness of his [Pitt’s] private character no one can form a just idea who had not the happiness of enjoying his acquaintance and society. He had a peculiar sweetness and benevolence of disposition, a kindness of heart, an unaffected ease, frankness, and simplicity, and a natural flow of spirits, which made his extraordinary intellectual powers as pleasant and fascinating in the common intercourse of life as they were commanding in the performance of official duties. His superiority was no less manifest when he conversed upon ordinary subjects, or joined in the mirth of a convivial party than when he presided in the Cabinet, or guided the deliberations of the House of Commons. Those who had only been accustomed to his dignified eloquence and grave parliamentary deportment, who had heard the decided and authoritative tone in which he delivered his own sentiments, and the sarcastic and indignant language in which he occasionally replied to his political antagonists, if they accidentally met him in private, could scarcely believe that the same person could possess that unassuming style of conversation, that playfulness, urbanity, and good-humour, which they then witnessed.”
This is another illustration of Pitt's two-sided personality juxtaposed in a magnificent way:
“A person of high rank, but of opposite politics, met Mr Pitt at a Christmas party for a few days at the country house of a common friend, and afterwards declared that he had never been so much mistaken in his idea of a private character. He pronounced him the pleasantest person in society he had ever known; and this testimony was the stronger, as Mr Pitt had been particularly hostile to the father of the person to whom I allude.” The name of the person was never directly stated, but at a guess, I would venture to say it was Lord North's son.
Pitt was a genius. I don't use that term lightly. He sincerely was a prodigy. His incredibly retentive memory, and off-the-chart intelligence, was combined with the sweetest nature:
“…the brilliancy of his imagination, and his talent for wit and repartee, were accompanied with a delicacy of sentiment and an attention to the feelings of others which prevented his saying anything, even in his most unguarded moments and unrestrained sallies, to give pain or offence to the most sensitive mind. These qualities rendered him as much the object of private affection as we have seen that he was of public confidence…Such was the mildness of his nature that he never expressed himself with harshness in speaking to his intimate friends of his political opponents, or even of those who had deserted his cause upon frivolous grounds, or for dishonourable reasons. He was always desirous of finding an excuse or palliation for the most unwarrantable conduct; and he was ever ready, perhaps too ready, to receive again into his confidence those who had treated him with insincerity or ingratitude.”
Not surprisingly, Tomline states that Pitt had no ear for music, nor much taste in drawings or paintings. Instead, Pitt was interested in architecture, and used to amuse himself with drawing a plan of the best possible house. An anecdote of this is below:
“When he was seventeen I went on the Norfolk tour with him, which was at that time a favourable excursion, and several days after our return he drew from memory a plan of one of the largest houses we had seen with a view of improving it."
Pitt's interest in sports and the countryside:
"While young he occasionally partook in field sports, but his mind was not of a cast to be occupied by such pursuits. He was fond of the country and enjoyed its scenery. At first, for the sake of health, he rented a furnished house with a small quantity of ground on Putney Heath; but in a place belonging to another he could feel but little interest, and the distance from London was so short that he could not be free from frequent interruption, and therefore in 1785 he bought a small house with 200 acres of land, called Hollwood Hill, about fifteen miles from London.”
In talking of Pitt's fondness for Hollwood, Tomline relates that Pitt afterwards purchased about the same quantity of contiguous land in addition to the previous 200 acres he originally purchased, and he enlarged the house to accompany four or five friends. He turned the road which passed close to the house, and he spent a great deal of his leisure time in planting and laying out the ground, and forming a piece of water nearby.
In reminiscing on the wild and picturesque land surrounding Hollwood, and Pitt's time there, he adds:
“It was delightful to see him at this his Sabine farm. After toiling in his room over revenue details or foreign despatches on which the fate of nations depended, he would walk out, and taking his spud in his hand grub up a thistle or a weed, or give directions about the removal of a shrub, or the turning of a walk, with as much earnestness and interest as if he had nothing else to occupy his thoughts. Instead of the First Minister of a great nation, he seemed to be a country gentleman with no other employment but to attend to the trifling disposition of a few acres of pleasure ground - he apparently felt as much anxiety to omit no means of improving his villa, as to promote the welfare of his country. Mr Pitt’s deep and accurate knowledge of the Greek and Latin languages has been noticed in speaking of the early part of his life; and after he became Minister a Homer or a Horace was always to be found upon his table in the midst of finance and political papers, and some classical book was his constant companion, if the weather compelled him to go in his carriage from London to Hollwood, or whenever he travelled.”
After Pitt's death, Tomline purchased his books for £1,900, and they formed a part of Tomline's library at Riby Grove, in Lincolnshire.
On the subject of women, Tomline writes that although Mr Pitt was never married, two overtures were mentioned to him: one was the French finance Minister Necker's daughter, and the other was the Duchess of Gordon's daughter Charlotte. Tomline did not believe Pitt had any inclination to marry either of those two women.
Tomline does, however, give an instance where Pitt's heart was involved:
“At a later period of life he showed a very marked attention to the daughter of a political friend [Auckland], at whose house he frequently visited, and he for some time hesitated whether he should make a proposal of marriage. At last he determined in the negative; but he was aware that though no declaration had been made, he had so far raised expectations that an explanation was due to the family…”
Tomline apparently wished that Pitt would have married:
“I have always greatly lamented that Mr Pitt did not marry early in life. No man could be more suited to the connubial [marital] state than he was; and I am confident that if he had shown his usual judgement in the selection of a wife, she would have added most essentially to his comfort and happiness. England might then have had to boast of a third William Pitt.”
Where's that time machine?!
Tomline on Pitt's financial embarrassments:
“Mr Pitt, from his first residence in college, showed a great indifference to his own pecuniary concerns; and when he came into office, his time was so completely devoted to his public duties that he found no leisure to attend to his private affairs.” He believed Pitt inherited £10,000 from his father, and the Duke of Rutland left him £3,000 as a legacy in 1787.
Tomline thought the debts were caused by impositions from tradesman and servants, which Pitt subjected himself to by inattention. Tomline used to look over the books kept by the house-steward. “I once told him [Pitt] that I thought some good might be effected by his giving his principal servant more power over the other servants, to which he answered, “That I never will do, for I should make him a tyrant, and the rest of the family slaves.”
On Pitt’s debts in 1801: "Some creditors instituted legal proceedings against him, and he was in danger of being left without furniture, books, clothes, carriage, or horses. It occurred to him that he had some pictures set with diamonds, and other things of the same sort, presents from foreign courts, freedom of cities and towns which had been sent to him." All these were sold, and Pitt also sold the reversionary interest in the pension, and the parliamentary grant of £4,000 a year. There was also a private subscription from some of Pitt's closest friends and political associates, which Pitt had the intention to pay back with interest. Unfortunately, Tomline states that this could never be done as Pitt would not have had enough money to live on if he did so.
It wasn't enough to discharge his mounting debts. Tomline writes:
"He [Pitt] next resolved, with that manly cheerfulness which never deserted him, to sell his favourite Hollwood."Although this relieved him of the most pressing difficulties, considerable debts remained - principally to his bankers Messrs. Coutts and Co.
Lastly, another quote merging Pitt's dual personality with his ardent love of his country:
“Where duty or the service of his country was concerned, his easiness of temper was changed into inflexible firmness.” He was a great man.
1. No. 35, XII. 2 - August 1903 - ‘Tomline’s Estimate of Pitt’ by Earl Rosebery, p. 1.
The Monthly Review, Vol. 12 (July - September 1903)