Arnold was educated at
Highgate School and
Magdalen College, Oxford, before gaining a
diploma in law from the
University of Westminster. He was called to the bar in 1985 and made a
silk in 2000. He was appointed to the High Court Chancery Division in 2008, becoming the judge in charge of the Patent Court in April 2013. In 2011, he criticized
copyright law as "incoherent." In 2016, he ruled that
Nestle could not trademark
KitKat Candy bars' shape. He was appointed to the Court of Appeal, effective 1 October 2019. In 2024, Arnold ruled that
Lenovo has to pay additional licence fees to
InterDigital. In 2025, Arnold concurred with a denying
Tesla Motors a licence. ==See also==