Aidan O’Neill QC

Matrix Chambers

While Brexit had been burning in the backs of everyone’s minds during 2019, Matrix Chambers’ Aidan O’Neill QC was holding the torch at the front. With a wide-ranging European, constitutional and public law practice both north and south of the border, he has overseen the biggest Brexit- related cases.

In December 2018, he was victorious before the Full Court (25 judges) of the European Court of Justice in the case of Wightman, to decide whether Article 50 could be revoked.

In September, O’Neill appeared before the 11-judge bench of the UK Supreme Court in Miller 2/Cherry representing Joanna Cherry QC. He persuaded it unanimously to uphold the ruling of the Inner House of the Court of Session regarding Boris Johnson’s prorogation of Parliament. With the then date for withdrawal from the EU approaching on 31 October, O’Neill had to act swiftly. As the fastest case ever in the Court of Justice, he helped see it through in just two months.