Iain Wilton joins the 25-strong agency having recently stepped down as head of communications and public affairs at Marylebone Cricket Club (MCC).
Wilton was a special adviser to Howard in the mid-1990s when he was employment secretary. He was also an aide to the former cabinet minister William Waldegrave. He went on to spend two years as head of public affairs at Sport England before joining MCC in 2001.
Quintus is headed up by founder and MD Chris Guyver.