Mary Arden, Lady Arden of Heswall

Arden's appointment to the Supreme Court of the United Kingdom, replacing her husband on the court, was announced in June 2018, to take effect on 1 October 2018. She was the only woman out of the eleven judges of the court between the retirement of Lady Black in January 2021 and the appointment of Lady Black's successor, Lady Rose in April 2021.

Mary Howarth Arden was born in Liverpool, the daughter of Lieutenant-Colonel Eric Cuthbert Arden, of Heswall, Cheshire, a solicitor who had served with the Royal Garrison Artillery, and Mary Margaret (née Smith). Her grandfather was a partner in Gamon Arden and Co., a Liverpool firm of solicitors. Her father and brother, Roger, joined the family firm which merged with Hill Dickinson in 2007. She was brought up in south Liverpool and educated at Huyton College. She read law at Girton College, Cambridge, where she gained a starred first and an LLM, and an LLM degree at Harvard Law School in 1970 as a Kennedy Scholar.

Her husband became a Lord Justice of Appeal in 1999. On 2 October 2000, she was also appointed to the Court of Appeal. The couple became the first married couple both to sit on the Court of Appeal.

By the time she retired in 2022, she was the eldest of the justices (Lord Lloyd-Jones was the second-eldest at 69). Following the retirement (and death) of Lord Kerr of Tonaghmore in 2020 she was the only remaining member to have held judicial office before 31 March 1995 and was thus allowed to retire at 75 instead of 70.

She was appointed to the High Court on 30 April 1993, becoming the first female High Court judge to be assigned to the Chancery Division. As is customary, she was appointed a Dame Commander of the Order of the British Empire (DBE) at the same time. Her husband joined the Queen's Bench Division in October 1993, making them the first married couple to sit on the High Court bench. That feat has now been matched by Sir Peter Openshaw and Dame Caroline Swift. Arden was chairman of the Law Commission from 1996-99.

She married Jonathan Mance (now Lord Mance, former Deputy President of the Supreme Court of the United Kingdom) in the Lady Chapel at Liverpool Cathedral in 1973; they have three children together, two daughters and a son. By virtue of her marriage, she is entitled to be styled The Lady Mance, but is instead known by her own judicial title.

She was called to the bar at Gray's Inn in 1971, and joined Lincoln's Inn in 1973. She practised at Erskine Chambers from 1971 to 1993, mainly in company law. She became a QC in 1986, and served as Attorney-General of the Duchy of Lancaster. She is an Honorary Fellow of Royal Holloway, University of London, and of Liverpool John Moores University.

Mary Howarth Arden, Baroness Mance, DBE, KC, PC (born 23 January 1947), known professionally as Lady Arden of Heswall, is a former Justice of the Supreme Court of the United Kingdom. Before that, she was a judge of the Court of Appeal of England and Wales.