Jonathan Philip Chadwick Sumption, Lord Sumption, OBE, PC, FSA, FRHistS, KC (born 9 December 1948), is a British author, medieval historian, barrister and former senior judge who sat on the Supreme Court of the United Kingdom between 2012 and 2018, and a Non-Permanent Judge of the Hong Kong Court of Final Appeal from 2019 to 2024.

He is the eldest of the four children of Anthony Sumption,[10] a decorated naval officer and barrister, and Hilda Hedigan; their marriage was dissolved in 1979.

[13][14][15] He was elected a fellow of Magdalen College, teaching and writing books on medieval history from 1971 to 1975 before leaving to pursue a career in law.

Sumption joined Brick Court Chambers in 1975, where he remained for the entirety of his commercial legal career as a barrister.

On 30 November 2007, when a practising barrister, Sumption successfully represented himself before Mr Justice Collins in a judicial review application in the Administrative Court concerning proposed development near his home at Greenwich.

[20][21] The Guardian once described him as being a member of the "million-a-year club", the elite group of barristers earning over a million pounds a year.

Byers became the only former Cabinet Minister to be cross-examined in the High Court in relation to his actions in modern times: the British Government won the case.

[37] Sumption's narrative history of the Hundred Years' War between England and France (of which five volumes have been published, between 1990 and 2023) has been widely praised as "earning a place alongside Steven Runciman's A History of the Crusades" according to Frederic Raphael, and as a work that "deploys an enormous variety of documentary material ... and interprets it with imaginative and intelligent sympathy" and is "elegantly written" (Rosamond McKitterick, Evening Standard); for Allan Massie it is "An enterprise on a truly Victorian scale ... What is most impressive about this work, apart from the author's mastery of his material and his deployment of it, is his political intelligence".

"[39] In 1974, he worked with Conservative MP Sir Keith Joseph at the Centre for Policy Studies, an economically liberal think-tank.

[40] He has said that an attempt to rapidly achieve gender equality in the Supreme Court through quotas or positive discrimination could end up discouraging the best applicants, as they would no longer believe that the process would select on merit, and "have appalling consequences for justice".

[41][42] He has criticised the judicial appointments process in the United States, where politicians quiz judicial appointees on their views, as "discreditable" and described former Attorney General for England and Wales Sir Geoffrey Cox's proposal for a similar system as, "one of the most ill-thought-out ideas ever to emerge from a resentful government frustrated by its inability to do whatever it likes".

[38] He believes that history should not be apologised for once perpetrators of injustices are no longer alive, describing apologies for events such as the Irish Famine and the Armenian genocide as "morally worthless", although saying that, "we have a duty to understand why things happened as they did" and there are "lessons to be learned".

[44] In the wake of the Black Lives Matter protests following the murder of George Floyd in May 2020 in Minneapolis, the United States, Sumption criticised the removal of monuments, arguing that people of the past did not share the values of the present and calling it "an irrational and absurd thing to do".

He argues that since the 1960s, but particularly in recent years, the courts have undermined the political processes and institutions of parliament by judging issues that should be decided by elected politicians and ministers.

He argues that political figures are more democratically accountable to the public for decisions they make, unlike judges who are unelected and difficult to remove from office.

[54] Sumption has been highly critical of the British government's lockdowns during the COVID-19 pandemic on civil libertarian grounds, seeing them as a slippery slope,[55][39] while also criticising the legal basis for their enactment and the enforceability of COVID-19 control measures.

"[62] Health experts have criticised his views, stating that the concept of "quality adjusted life years" is primarily useful for debates on the allocation of scarce healthcare resources, and may not be useful for discussion of a nationwide lockdown.

[63] In July 2021, Full Fact concluded in a fact-checking article that Sumption had "made several mistakes with Covid-19 data when talking about the disease" on BBC Radio 4's Today programme.

[65] In February 2025 Sumption told the Guardian that he thought there was an arguable case that Israel’s conduct in Gaza was genocidal.