The friendship between Pitt's niece Lady Hester Stanhope and Pitt's last private secretary William Dacres Adams continued long after Pitt's death. Although they first met in 1804, they quickly grew close to the point that Dacres Adams named his first-born son William Pitt Adams, with Lady Hester Stanhope acting as the boy's godmother.
Sadly, Pitt's death at the end of January 1806 brought an end to one of the happiest times in both of their lives. Lady Hester was left in the difficult predicament of not knowing where she was going to be living, and Adams was temporarily without employment. Many years later, Adams would tell Lord Stanhope that Pitt's death was "the first great affliction" of his life. 
In the immediate aftermath of Pitt's decease, Lady Hester was staying at George Canning's house at South Hill, and on Sunday, 26 January 1806, she poured out her feelings to Adams:
“…I am so anxious about Monday much less on my own account than upon another score, for be my fate what it may, I am prepared to meet the worst conscious that I have already received from Providence many blessings I do not deserve. Therefore, I have no right to expect more, yet my mind ever will retain its independence. You always temper the blast to the Shorn Lamb, and he has blessed me with a Spirit equal to bear any misfortune (unconnected with remorse) if I can support myself…You have no idea of the consolation it is to me that I received the last blessing of that beloved angel and that when forbid to see him (because it was thought he wd not know me) I took my own way and disobeyed continual commands. My voice recalled his scattered senses, and he was perfectly collected the Whole time I was with him, and when I departed and his ideas again became confused he continued to name me with affection. This proud prominence over the rest of the world will compensate me for many future sorrows which his loss must entail upon me.” 
She was right, for indeed Lady Hester Stanhope's life would never be the same after the loss of her beloved uncle. Around the time she later moved to Montagu Square, Lady Hester wrote to Adams, not forgetting his loyalty and kindness to her in a time of need:
“…Believe me, I shall ever consider you amongst those few friends who are endeared to me by their sincere and disinterested attachment to that beloved angel [Pitt] who is no more. It would wound my feelings extremely if I c[oul]d suppose you thought because the tie is alas broken which first connected us, that let my fate in future be what it may, I s[houl]d ever lose sight of one who has uniformly shown him [Pitt] worthy of the confidence placed in him, and deserving of the friendship of the first mortals. This of itself wd be reason sufficient for me to continue to respect you as I have hitherto done. Did not the recollection of the many little kindnesses you have shewn me and my brothers have separate claims upon the friendship and good wishes of your ever sincere Friend, HLS.” 
When Lady Hester and her 'female companion' Miss Elizabeth Williams left England permanently in 1810, she inevitably lost touch with William Dacres Adams - but she never forgot him. Seven years later, in 1817, she asked her physician Dr. Meryon to write a letter to Adams on her behalf, and she dictated it to him. She was not a woman to easily forget those who hurt her, or helped her, through times of crisis. Adams was no exception. She wrote to Adams, reminding him that she “…never can forget that you were a kind friend to us in misfortune.” 
For his part, Adams retained his allegiance to Lady Hester throughout his long life. When in old age, Adams admitted to Earl Stanhope that he had heeded Lady Hester Stanhope's injunctions just after Pitt's death, and had kept a large stash of Pitt's private and political papers "in a cupboard the last half a century." 
It is fortunate for posterity that he heeded her advice, for many of Pitt's private papers in Adams' safekeeping have now been transferred by his descendants to The British Library. None of the papers have the trademark 'GL' to denote George, the Bishop of Lincoln's "approval" for them to be kept. Presumably, these were some of the papers that have escaped the flames of decimation.
1. William Dacres Adams to Philip Henry (5th Earl) Stanhope. Kent History & Library Centre, Stanhope of Chevening Manuscripts, Pitt MSS: U1590/C405/2.
2. Lady Hester Stanhope to William Dacres Adams. Sunday Night, 26 January 1806. The British Library. Dacres Adams MSS: 89036/2/1, Letters 1-29, ff. 10-10(i).
3. Lady Hester Stanhope to William Dacres Adams. [undated, but between 1806-8] The British Library. Dacres Adams MSS: 89036/2/3, f. 80.3.
4. Lady Hester Stanhope (in Dr. Meryon's handwriting) to William Dacres Adams. Mount Lebanon, January 3, 1817. The British Library. Dacres Adams MSS: 89036/2/3, f. 81.
5. William Dacres Adams to Philip Henry (5th Earl) Stanhope. Kent History & Library Centre, Stanhope of Chevening Manuscripts, Pitt MSS: U1590/C405/2.