After succeeding to his father's estates, he came to Court. He was present at the
Field of the Cloth of Gold in 1520, where he gained royal favour through his skill in
jousting. He was
knighted on 20 August 1534, and appointed Vice-Treasurer and General Receiver of Ireland. He sat in the
Irish House of Commons in the Parliament of 1536–7. In a letter from the
Lord Chief Justice of Ireland,
Gerald Aylmer to
Thomas Cromwell in August 1535 he was described as "the man that prevented the total ruin and desolation of the Kingdom". In 1536, he and
John Barnewall, 3rd Baron Trimlestown beat back an assault by the O'Connor clan on Carbury by burning several villages in
Offaly and carrying away great spoil. The next year he made so effective a speech in support of establishing the King's authority in opposition to that of the
Pope that he persuaded the
Parliament of Ireland to pass the two requisite Acts, the
Act of Appeals 1537 and the
Act Authorising the King, his Heirs and Successors to be Supreme Head of the Church of Ireland 1537. As a result of this, many religious houses were in 1539 surrendered to King
Henry VIII. Brabazon himself was granted the lands of the Abbey of St Thomas, between present-day Thomas Street in
Dublin and the
River Liffey: here he built his townhouse Thomas Court. The Abbey's lands included
Kilruddery, which later became, and remains, the family's principal seat. , home of Brabazon's descendants, the Earls of Meath, present day For his good services to the Crown he was, on 1 October 1543, constituted Lord Justice of Ireland, and he was again appointed to the same office on 1 April 1546. In the same year, he drove Patrick O'More and Brian O'Connor from Kildare. In April 1547 he was elected a member of the
Privy Council of Ireland. In the spring of 1548 he assisted the
Lord Deputy of Ireland in subduing a rebellion raised in
Kildare by the sons of
Thomas Eustace, 1st Viscount Baltinglass. He was for the third time made Lord Justice on 2 February 1549. In August 1550, he subdued
Cahir mac Art Kavanagh, head of the powerful
MacMurrough-Kavanagh dynasty and the dominant Gaelic magnate in
Leinster. Cahir, after making submission and renouncing his Irish title
The MacMurrough, received a
royal pardon, and the new title Baron of Ballyann. ==Death==