Answer #1: . . . . . Yes
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Answer #2:
In the absence of any simple declarative published statement, you have to
explore whatever IS available, looking for clues.
"Kirsty Allsopp is the daughter of the former chairman of Christie's, Charles Henry Allsopp, 6th Baron Hindlip, and Fiona Victoria Jean Atherley (née McGowan, born 1947)." -- 'Charles' and 'Henry' are, shall we say, 'rare' given names among Jews.
-- So are 'Fiona', 'Victoria', and 'Jean'.
-- 'McGowan' evolves as an Anglicization of the original Gaelic language
personal description or nickname "gobha", meaning in English language
"blacksmith". The name is a surname of ancient Gael royals, dating from
the 12th Century and earlier, and is equally, shall we say, 'rare' as a family
name among Jews.
-- Few Jews in the mid 20th Century have been granted peerages. Even fewer
are the sixth in any privileged line in the UK.
"She has a younger brother Henry William, and two younger sisters,
Sofie and Natasha." -- As noted above, 'Henry' is rare as a given name among Jews, as is 'William'.
-- 'Sofie' and 'Natasha' are Russian names, and not particularly common among Jews.
I'll be interested to see what source or reference the contributor of Answer #1
can cite. So far, none have been cited, and the clues I've been able to find
seem to tend toward the negative.
Kirstie Allsopp's birth name is Kirstie Mary Allsopp.
Sofie Allsopp's birth name is Sophia Atherley Allsopp.
Dan Allsopp died in 1921.
Dan Allsopp was born in 1871.
Herbert Allsopp was born in 1855.
Herbert Allsopp died in 1920.
Ted Allsopp was born in 1926.
Frederic Allsopp died in 1928.
Frederic Allsopp was born in 1857.
Thomas Allsopp was born in 1880.
Thomas Allsopp died in 1919.
Elijah Allsopp was born in 1877.