The retirement was announced by the Lord Speaker at the start of business:
https://parliamentlive.tv/event/index/b57d67b4-93e0-4885-8bff-2db2ef0f3d99?in=15:07:20Unusually, there was no prior notification in the House of Lords Business document. Presumably the notice of retirement has only just been submitted.
Lord Young of Graffham is 90 (born 27 February 1932). He was created a life peer in 1984, entering the Cabinet immediately, initially as Minister without Portfolio.