The idea for celebrating house achievements and house spirit came from the Second Master, Simon Lockyer, in 2011. He sought advice on the benefactors who gave their names to the Senior School houses. Only one, founder Dr William Smith, had a coat of arms, and so a suggestion was put forward drawing largely on elements of the school coat of arms against a background of the house colour.

Dr William Smith was granted his coat of arms in 1711, the most prominent element being the golden lion which was the obvious choice against a red background.

Alderman Joseph Whitcombe, who served on the town council and was mayor in 1881-82, was a popular public servant and philanthropist. The star and crescent, representing Portsmouth, reflects the Alderman's dedication to public service.

Thomas Latter's bequest paid for scholarships to Oxford and Cambridge for students intending to take Holy Orders. The coat of arms of Christ Church College, Oxford (which appears in the PGS arms because of the College’s role as Dr William Smith's trustees and continuing part in the governance of the School) was used against a yellow background.

Finally, the flag for Grant House, named after the School's re-founder, Canon Edward Pierce Grant, was based on the sword element from the crest for the Portsmouth Anglican Diocese, against a blue background. Canon Grant was Vicar of Portsmouth and also played a major role in the development of education in the town, helping to establish both the High School and a college that was to evolve into the University of Portsmouth.

The flags received their first public appearance down the High Street during the "March Through the Arch" leavers' procession of 2012.  

(Simon Lockyer has recently been appointed CEO and principal of the British School of Milan, following a successful nine years as Head of The Royal Hospital School.)