The reluctant Baronet's obit is in the Times of 31 May 2021.
The obit also mentions the adoption of his first wife's dau from a prev union (Juliet b 194_), and she's listed as such in Burke's Peerage & Baronetage 2003, but not mentioned in Drebrett's 2019.
Interestingly, the first mention of his marriages and daus in Debrett is
in the 1976 edn (I have a complete run of DPB between 1970 and 2019, as
well as some earlier edns between 1897 and 1965).
EXTRACT
OBITUARY
Sir Leslie Marr, Bt obituaryColourful landscape artist and Formula One racing driver who was heir to a shipbuilding family and refused to acknowledge his title
...
In 1948 he married [Dinora Delores] Mendelsohn [b 1924 reg Q2 London] and adopted her daughter Juliet......Leslie Lynn Marr was born in Durham in 1922, the only child of Colonel John Marr OBE, a Flanders veteran, and his wife Amelia (nee Thompson), known as May, an excellent markswoman and a pioneering motorist. His parents' marriage had been a union of Wearside family shipyards and they assumed that young Leslie would follow in their footsteps....
...in 1931 he learnt that his 53-year-old father had died from pneumonia. His paternal grandfather, Sir John Marr, who in 1919 had been awarded a baronetcy by David Lloyd George, died within the year and ten-year-old Leslie inherited a title that he refused to acknowledge....
...His first marriage had been formally dissolved in 1956 and in 1962 he married Lynn Moynihan... They had two daughters, Joanne, a luxury-yacht broker in the south of France, and
Rebecca, a chef who died from breast cancer in [30 March] 2016.... The marriage was dissolved in 1998 and the following year he met Maureen Monk, a former actress, who accompanied him on many painting expeditions. They were married in 2002 and she survives him....
Sir Leslie Marr, Bt, artist and racing driver, was born on August 14, 1922. He died on May 4, 2021, aged 98https://www.thetimes.co.uk/article/sir-leslie-marr-bt-obituary-2hh6tqx8d