It was probably during his stay in Paris that he came under the influence of George Buchanan, to whom, in a letter to Peter Young, tutor of James VI, he refers in very eulogistic terms as his 'master'.
Soon after the accession of Elizabeth, in 1558, Randolph was acting as an agent of the English government in Germany, but in a few months returned to England; and, probably soon afterwards, bought a farm in Kent—"the house where he was born".
Doubtless his acquaintance with the Scottish Protestants in Paris suggested to Elizabeth the employment of Randolph in the task of bringing the Earl of Arran, who had been compelled to flee from France, from Geneva to England.
[5] He left for London on 25 November, but was again sent to Scotland in March 1560, where his representations had considerable influence in encouraging the Protestants against the queen-regent, and in effecting an understanding between them and Elizabeth.
Although by no means a match for Maitland of Lethington as a diplomatist, the fact that he possessed the confidence of the Protestant party enabled him to exercise no small influence in Scottish politics.
His numerous letters are among the most valuable sources of information for this period; they abound in interesting details regarding the Queen of Scots and her court, and the political plots and social intrigues.
[8] Instead of meeting Elizabeth in England, in the autumn of 1562 Randolph accompanied the Queen of Scots, who professed for him a warm friendship, in an expedition to the north of Scotland.
This resulted in the defeat and death of George Gordon, 4th Earl of Huntly; and Randolph even took part in the campaign, "being ashamed to sit still where so many were occupied".
Randolph again received instructions to press for a marriage "with the Earl of Leicester or some other; and if he find it so far passed as it cannot be revoked, then he shall...declare, how much it shall miscontent her Majesty".
[19] One of Randolph's Scottish contacts, Alexander Clark sent him a letter teasing him about their relationship in a joke using nonsense words; "And as to your mistress Marie Beton, she is both darimpus and sclenbrunit, and you in like manner without contrebaxion or kylteperante, so you are both worth little money.
On 16 January 1566 he reported Mary withheld the "Matrimonial crown" from Darnley and was now pregnant:It is now spoken for certain that she is with child; and, as it is said, she felt it stir in her belly upon new year's day.
[22]On 14 February 1566 Randolph wrote to the Earl of Leicester that he was unable and unwilling to commit his opinions on Mary's actions on paper for fear of appearing "malicieus foolyshe and unadvised".
[23] In February 1566 he was accused by Mary of having assisted Moray and her rebellious subjects during the Chaseabout Raid with a gift of three thousand crowns, and was required to quit the country within six days.
Randolph was sent on his last mission to Scotland in January 1586, accompanied by Thomas Mills, with instructions for the negotiation of a treaty between the two kingdoms, to which he succeeded in obtaining the signature of James VI despite the efforts of a French diplomat Charles de Prunelé, Baron d'Esneval.
[27] In August 1586 Randolph and the Scottish ambassador in London, Archibald Douglas, sent male deer and huntsmen to serve James VI at the park of Falkland Palace.
Randolph wrote:I have sent the Kynge two hunting men, verie good and skillful, with one footman, that can hoop, hollow and crye, that all the trees in Fawkland will quake for fear.
[29]Randolph held the joint offices of Chamberlain of the Exchequer and Master of the Post till his death, which took place in his house in St. Peter's Hill, near Thames Street, London, on 8 June 1590, when he was in his sixty-seventh year.
In July 1593 the Scottish ambassador in London, with Roger Aston, insisted that the deceased diplomat Thomas Randolph had promised in 1586 the sum of £5000 yearly would be paid to James VI as a subsidy or annuity.
Before the marriage he received, on 1 October 1571, an assignment from Thomas Walsingham and William Crowner of letters patent of the custody of the manor and hundred of Middleton and Merden, at the rent of 100 pounds per annum, to be paid to his intended wife.