Robert Dudley was counted among Elizabeth's special friends by Philip II's envoy to the English court a week before Queen Mary's death.
On 18 November 1558, the morning after Elizabeth's accession, Dudley witnessed the surrender of the Great Seal to her at Hatfield.
He became Master of the Horse on the same day.
This was an important court position entailing close attendance on the sovereign.
It suited him, as he was an excellent horseman and showed great professional interest in royal transport and accommodation, horse breeding, and the supply of horses for all occasions.
Dudley was also entrusted with organising and overseeing a large part of the Queen's coronation festivities.

In April 1559 Dudley was elected a Knight of the Garter.
Shortly before, Philip II had been informed:
Lord Robert has come so much into favour that he does whatever he likes with affairs and it is even said that her majesty visits him in his chamber day and night.
People talk of this so freely that they go so far as to say that his wife has a malady in one of her breasts and the Queen is only waiting for her to die to marry Lord Robert ... Matters have reached such a pass ... that ... it would ... be well to approach Lord Robert on your Majesty's behalf ... Your Majesty would do well to attract and confirm him in his friendship.

Within a month the Spanish ambassador, Count de Feria, counted Robert Dudley among three persons who ran the country.
Visiting foreigners of princely rank were bidding for his goodwill.
He acted as official host on state occasions and was himself a frequent guest at ambassadorial dinners.
By the autumn of 1559 several foreign princes were vying for the Queen's hand; their impatient envoys came under the impression that Elizabeth was fooling them, "keeping Lord Robert's enemies and the country engaged with words until this wicked deed of killing his wife is consummated." "
Lord Robert", the new Spanish ambassador de Quadra was convinced, was the man "in whom it is easy to recognise the king that is to be ... she will marry none but the favoured Robert."
Many of the nobility would not brook Dudley's new prominence, as they could not "put up with his being King."
Plans to kill the favourite abounded, and Dudley took to wearing a light coat of mail under his clothes.
Among all classes, in England and abroad, gossip got under way that the Queen had children by Dudley—such rumours never quite ended for the rest of her life.
Robert Dudley was counted among Elizabeth's special friends by Philip II's envoy to the English court a week before Queen Mary's death. On 18 November 1558, the morning after Elizabeth's accession, Dudley witnessed the surrender of the Great Seal to her at Hatfield. He became Master of the Horse on the same day. This was an important court position entailing close attendance on the sovereign. It suited him, as he was an excellent horseman and showed great professional interest in royal transport and accommodation, horse breeding, and the supply of horses for all occasions. Dudley was also entrusted with organising and overseeing a large part of the Queen's coronation festivities.
In April 1559 Dudley was elected a Knight of the Garter. Shortly before, Philip II had been informed:
Lord Robert has come so much into favour that he does whatever he likes with affairs and it is even said that her majesty visits him in his chamber day and night. People talk of this so freely that they go so far as to say that his wife has a malady in one of her breasts and the Queen is only waiting for her to die to marry Lord Robert ... Matters have reached such a pass ... that ... it would ... be well to approach Lord Robert on your Majesty's behalf ... Your Majesty would do well to attract and confirm him in his friendship.
Within a month the Spanish ambassador, Count de Feria, counted Robert Dudley among three persons who ran the country. Visiting foreigners of princely rank were bidding for his goodwill. He acted as official host on state occasions and was himself a frequent guest at ambassadorial dinners. By the autumn of 1559 several foreign princes were vying for the Queen's hand; their impatient envoys came under the impression that Elizabeth was fooling them, "keeping Lord Robert's enemies and the country engaged with words until this wicked deed of killing his wife is consummated." "Lord Robert", the new Spanish ambassador de Quadra was convinced, was the man "in whom it is easy to recognise the king that is to be ... she will marry none but the favoured Robert." Many of the nobility would not brook Dudley's new prominence, as they could not "put up with his being King." Plans to kill the favourite abounded, and Dudley took to wearing a light coat of mail under his clothes. Among all classes, in England and abroad, gossip got under way that the Queen had children by Dudley—such rumours never quite ended for the rest of her life.
Robert Dudley, 1st Earl of Leicester