From the Court Circular page of the Buckingham Palace website:
9 February 2017: His Excellency Mr. Choe Il was received in audience by The Queen today and presented the Letters of Recall of his predecessor and his own Letters of Credence as Ambassador from the Democratic People’s Republic of Korea to the Court of St. James’s. Mrs. Kim Yong Ae was also received by Her Majesty.
As reported by KCNA:
Pyongyang, February 12 (KCNA) — Choe Il, DPRK ambassador to UK, presented his credentials to Queen Elizabeth II on February 9. The queen hoped that the relations between the two countries would develop on good terms.
The previous ambassador, Hyon Hak-bong, was recalled to Pyongyang in 2016