From the Telegraph of 29 May 2021: MILLETT Peter Julian Millett,
Baron Millett of St Marylebone in the City of Westminster, PC, OH, died peacefully at home on 27th May 2021. Beloved husband of Ann, father of Richard and Andrew, father-in-law to Patricia and Vanessa, and grandfather to Alexia, Edward, Eliza, James and Isabella. There will be a private funeral and prayers, with a memorial service to follow.
He was s of (Isaac Moses) Denis MILLETT 1899-1965 by his 1929 m reg Q3 Lancs to Adele Yetta WEINBERG 1908-97. He m 1959 Ann Mireille d of David HARRIS of London and had three sons.
I surmise OH refers to 'Old Harrovian'