On 9 November 1838 Phillips was elected mayor of Newport, and became a figure of the Newport Rising. On 4 November 1839 was in charge of the town when John Frost, at the head of seven thousand chartists, entered it with the intention of releasing Henry Vincent from gaol. While reading the Riot Act from the Westgate Inn he was wounded with slugs in the arm and hip.
A company of the 45th Regiment of Foot then fired on the crowd, which was completely routed, seventeen being killed and about thirty wounded. On 9 December Phillips was knighted to mark his "individual exertions in maintaining her majesty's authority". On 26 February 1840 he was voted the freedom of the City of London, and admitted on 7 April.
Phillips was called to the bar at the Inner Temple on 10 June 1842. Shortly afterwards he set off on a tour of parts of Europe and the Middle East. He wanted to take a draughtsman, and on the recommendation of David Roberts employed Richard Dadd.
Roberts knew Dadd's father. The journey, via Venice, Greece and Egypt, saw Dadd suffer a breakdown, and he returned to England, leaving Phillips in Paris, in May 1843, suffering from mental illness. Having stabbed his father to death, he was confined to Bethlem Hospital as insane.
Phillips was named a Queen's Counsel on 17 February, and a bencher of his inn on 5 May 1865. His principal practice lay in parliamentary committees, and many lawsuits were referred to him for arbitration. In Monmouthshire he acquired coal-mines, and became a large landed proprietor in Wales.
Phillips played a major part in the success of Brecon College. While living simply, he gave large sums to charities. At Court-y-bella, near Newport, he built and maintained schools for the education of the colliers.
Phillips died of paralysis at 77 Gloucester Place, Portman Square, London, on 26 May 1867, and was buried at Llanellan. He was not married.
He was an active member of the governing bodies of King's College London, and the Church Institution, and president of the council of the Society of Arts. In 1848 he became a member of the National Society, and devoted time and labour to the work of national education.