Refer to the passage below and then answer the question afterwards in the same language as the passage:

Passage: Hubert Miles Gladwyn Jebb, 1st Baron Gladwyn  known as Gladwyn Jebb (25 April 1900 – 24 October 1996), was a prominent British civil servant, diplomat and politician as well as the Acting Secretary-General of the United Nations for a little over three months.

Question: What Baron rank was Hubert Miles Gladwyn Jebb?
1st