He was knighted about 1577 and became the Justice Clerk. On 1 July 1584 he was promoted as a Lord Ordinary as a
Senator of the College of Justice, in place of Sir
Richard Maitland of Lethington. He was not averse to the conspiracies of the period and was one of the conspirators involved in the notorious
Raid of Ruthven, and
Godscroft represents him as extremely violent on the occasion. Sir Lewis does not seem, however, to have shared in the ruin which attended his co-conspirators, joining the College of Justice in 1584. He bore a principal part in the downfall of the
Earl of Arran, and the return of the banished Lords, although he was despatched by the former, then ignorant of his intentions, to accuse the latter at the court of Queen
Elizabeth I of England. Gray received a
New Year's Day gift of silver plate from Elizabeth in January 1585. In March 1585 he was sent as ambassador to Elizabeth I to discuss border matters. His servant John Graham wrote to him that his wife and son James were well, and his cousin Thomas Bannatyne had spoken to the king and treasurer for funding and obtained 600 crowns, and 500
merks for his wife, Margaret Livingstone. Bannatyne wanted Bellenden to silk leggings for him and Bible for his wife, and a length of "best coloured" green stemming cloth. James VI instructed him to thank
Sir Philip Sidney for the present of a lion hound, and asked him to the fairest and youngest bloodhound he could afford. He travelled back to Scotland with the English diplomat
Edward Wotton in May. He was in
Stirling in November 1585 when the banished Lords surprised
James VI and Arran there. The latter intended to have slain Bellenden, the
Master of Gray, and the Secretary, "but they drew to their armes and stude on their awn defence," and Arran had too much on his hands with his enemies without the walls to attack them. In 1586 he was Keeper of
Blackness Castle. In February 1587 he wrote to
Lord John Hamilton about
Alexander Stewart, a diplomat who was involved in failed negotiations to save the life of Mary, Queen of Scots. In August 1587, Bellenden went on the King's progress to
Inchmurrin and Dumbarton, and met
Richard Douglas at
Hamilton. On 22 November 1587 he was appointed Keeper of
Linlithgow Castle. On 24 December 1587 he was appointed (with his cousin Patrick, a son of
Patrick Bellenden of
Evie) Clerk of the Coquet of Edinburgh. This was a kind of customs official. Bellenden seems to have been useful in procuring the consent of the clergy to the Act whereby the temporalities of the prelacies were annexed to the Crown in 1587, and was the same year named one of the Commissioners "for satisfying the clergy of the lyferents." In 1589 he accompanied King
James VI in his matrimonial excursion to
Norway.
James Melville of Halhill mentions that Bellenden did not sail in the king's ship, but in one of three other ships, along with
John Carmichael, the
Provost of Lincluden,
William Keith of Delny,
George Home,
James Sandilands, and
Peter Young. James VI wrote from
Oslo on 1 December 1589 to
John, Lord Hamilton asking him to conclude a lawsuit with Bellenden, who the king described as "a man here that I am so much beholden to at this time". He was sent the following spring as Ambassador to the court of Elizabeth, to formally announce the wedding and ask for funds for the royal households. He was given 666
Danish dalers from the queen's dowry to fund this diplomatic mission. According to
David Calderwood, Bellenden was sent to England to ask for English ships to assist the royal fleet during the voyage from Denmark. Bellenden was in London by 6 April 1590, he returned in May 1590 without a payment of the
annual subsidy money that Elizabeth had begun to usually pay to James VI. King James gave him £2,000
Scots. ==Death==