[1] Her father, Bernard, an economics lecturer and chartered accountant, was born in 1929 to a Polish-Jewish family that emigrated to the United Kingdom prior to the Second World War while her mother, Barbara (died 2020), was a community doctor in the National Health Service who converted to Judaism upon marriage.

[2][3] Alexander was educated at Channing School in Highgate, London,[4] and later studied law and sociology from Cardiff University, where she served as president of the student union.

[14] Following Labour's landslide victory in the 2024 general election, Starmer accompanied her husband to Buckingham Palace for his appointment as prime minister by King Charles III.

[16] The Daily Telegraph reported in September 2024 that Starmer had accepted two free tickets to attend an Eras Tour concert by the American singer Taylor Swift at Wembley Stadium earlier that year.

[17] In the same month, her husband faced accusations of breaking parliamentary rules by not declaring £5,000 worth of clothes bought for her by the Labour donor Lord Alli.