Rob Firth has left HOK amid a restructuring at the AJ100 ranked big hitter
The high-profile director departed in March after joining the company two years ago from Austin-Smith:Lord.
The former practice development head left as HOK devolved responsibility for the role to all of its London directors.
Firth joined HOK in January 2011 with a brief to grow the practice by expanding into new markets and sectors in the UK and abroad.
In the past two years major wins at HOK have included a role masterplanning Gatwick Airports £1 billion overhaul and the transformation of a seventeenth century convent and church in Sicily.